summaryrefslogtreecommitdiff
path: root/include/trace
AgeCommit message (Collapse)Author
2012-01-17Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: (62 commits) Btrfs: use larger system chunks Btrfs: add a delalloc mutex to inodes for delalloc reservations Btrfs: space leak tracepoints Btrfs: protect orphan block rsv with spin_lock Btrfs: add allocator tracepoints Btrfs: don't call btrfs_throttle in file write Btrfs: release space on error in page_mkwrite Btrfs: fix btrfsck error 400 when truncating a compressed Btrfs: do not use btrfs_end_transaction_throttle everywhere Btrfs: add balance progress reporting Btrfs: allow for resuming restriper after it was paused Btrfs: allow for canceling restriper Btrfs: allow for pausing restriper Btrfs: add skip_balance mount option Btrfs: recover balance on mount Btrfs: save balance parameters to disk Btrfs: soft profile changing mode (aka soft convert) Btrfs: implement online profile changing Btrfs: do not reduce profile in do_chunk_alloc() Btrfs: virtual address space subset filter ... Fix up trivial conflict in fs/btrfs/ioctl.c due to the use of the new mnt_drop_write_file() helper.
2012-01-16Btrfs: space leak tracepointsJosef Bacik
This in addition to a script in my btrfs-tracing tree will help track down space leaks when we're getting space left over in block groups on umount. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-01-16Btrfs: add allocator tracepointsJosef Bacik
I used these tracepoints when figuring out what the cluster stuff was doing, so add them to mainline in case we need to profile this stuff again. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2012-01-12vmscan/trace: Add 'file' info to trace_mm_vmscan_lru_isolate()Tao Ma
In trace_mm_vmscan_lru_isolate(), we don't output 'file' information to the trace event and it is a bit inconvenient for the user to get the real information(like pasted below). mm_vmscan_lru_isolate: isolate_mode=2 order=0 nr_requested=32 nr_scanned=32 nr_taken=32 contig_taken=0 contig_dirty=0 contig_failed=0 'active' can be obtained by analyzing mode(Thanks go to Minchan and Mel), So this patch adds 'file' to the trace event and it now looks like: mm_vmscan_lru_isolate: isolate_mode=2 order=0 nr_requested=32 nr_scanned=32 nr_taken=32 contig_taken=0 contig_dirty=0 contig_failed=0 file=0 Signed-off-by: Tao Ma <boyu.mt@taobao.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10Merge branch 'writeback-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux * 'writeback-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: move MIN_WRITEBACK_PAGES to fs-writeback.c writeback: balanced_rate cannot exceed write bandwidth writeback: do strict bdi dirty_exceeded writeback: avoid tiny dirty poll intervals writeback: max, min and target dirty pause time writeback: dirty ratelimit - think time compensation btrfs: fix dirtied pages accounting on sub-page writes writeback: fix dirtied pages accounting on redirty writeback: fix dirtied pages accounting on sub-page writes writeback: charge leaked page dirties to active tasks writeback: Include all dirty inodes in background writeback
2012-01-10Merge branch 'akpm' (aka "Andrew's patch-bomb")Linus Torvalds
Andrew elucidates: - First installmeant of MM. We have a HUGE number of MM patches this time. It's crazy. - MAINTAINERS updates - backlight updates - leds - checkpatch updates - misc ELF stuff - rtc updates - reiserfs - procfs - some misc other bits * akpm: (124 commits) user namespace: make signal.c respect user namespaces workqueue: make alloc_workqueue() take printf fmt and args for name procfs: add hidepid= and gid= mount options procfs: parse mount options procfs: introduce the /proc/<pid>/map_files/ directory procfs: make proc_get_link to use dentry instead of inode signal: add block_sigmask() for adding sigmask to current->blocked sparc: make SA_NOMASK a synonym of SA_NODEFER reiserfs: don't lock root inode searching reiserfs: don't lock journal_init() reiserfs: delay reiserfs lock until journal initialization reiserfs: delete comments referring to the BKL drivers/rtc/interface.c: fix alarm rollover when day or month is out-of-range drivers/rtc/rtc-twl.c: add DT support for RTC inside twl4030/twl6030 drivers/rtc/: remove redundant spi driver bus initialization drivers/rtc/rtc-jz4740.c: make jz4740_rtc_driver static drivers/rtc/rtc-mc13xxx.c: make mc13xxx_rtc_idtable static rtc: convert drivers/rtc/* to use module_platform_driver() drivers/rtc/rtc-wm831x.c: convert to devm_kzalloc() drivers/rtc/rtc-wm831x.c: remove unused period IRQ handler ...
2012-01-10tracepoint: add tracepoints for debugging oom_score_adjKAMEZAWA Hiroyuki
oom_score_adj is used for guarding processes from OOM-Killer. One of problem is that it's inherited at fork(). When a daemon set oom_score_adj and make children, it's hard to know where the value is set. This patch adds some tracepoints useful for debugging. This patch adds 3 trace points. - creating new task - renaming a task (exec) - set oom_score_adj To debug, users need to enable some trace pointer. Maybe filtering is useful as # EVENT=/sys/kernel/debug/tracing/events/task/ # echo "oom_score_adj != 0" > $EVENT/task_newtask/filter # echo "oom_score_adj != 0" > $EVENT/task_rename/filter # echo 1 > $EVENT/enable # EVENT=/sys/kernel/debug/tracing/events/oom/ # echo 1 > $EVENT/enable output will be like this. # grep oom /sys/kernel/debug/tracing/trace bash-7699 [007] d..3 5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000 bash-7699 [007] ...1 5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000 ls-7729 [003] ...2 5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000 bash-7699 [002] ...1 5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000 grep-7730 [007] ...2 5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000 Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10mm-tracepoint: rename page-free eventsKonstantin Khlebnikov
Rename mm_page_free_direct into mm_page_free and mm_pagevec_free into mm_page_free_batched Since v2.6.33-5426-gc475dab the kernel triggers mm_page_free_direct for all freed pages, not only for directly freed. So, let's name it properly. For pages freed via page-list we also trigger mm_page_free_batched event. Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-10Merge branch 'for_linus' into for_linus_mergedTheodore Ts'o
Conflicts: fs/ext4/ioctl.c
2012-01-08Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap: (36 commits) mfd: Clearing events requires event registers to be writable for da9052-core mfd: Fix annotations in da9052-core gpiolib: Mark da9052 driver broken mfd: Declare da9052_regmap_config for the bus drivers MFD: DA9052/53 MFD core module add SPI support v2 MFD: DA9052/53 MFD core module regmap: Add irq_base accessor to regmap_irq regmap: Allow drivers to reinitialise the register cache at runtime regmap: Add trace event for successful cache reads regmap: Allow regmap_update_bits() users to detect changes regmap: Report if we actually handled an interrupt in regmap-irq regmap: Fix rbtreee build when not using debugfs regmap: Provide debugfs dump of the rbtree cache data regmap: Do debugfs init before cache init regmap: Suppress noop writes in regmap_update_bits() regmap: Remove indexed cache type regmap: Drop check whether a register is readable in regcache_read regmap: Properly round cache_word_size regmap: Add support for 10/14 register formating regmap: Try cached read before checking if a hardware read is possible ...
2012-01-06Merge branch 'sched-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (40 commits) sched/tracing: Add a new tracepoint for sleeptime sched: Disable scheduler warnings during oopses sched: Fix cgroup movement of waking process sched: Fix cgroup movement of newly created process sched: Fix cgroup movement of forking process sched: Remove cfs bandwidth period check in tg_set_cfs_period() sched: Fix load-balance lock-breaking sched: Replace all_pinned with a generic flags field sched: Only queue remote wakeups when crossing cache boundaries sched: Add missing rcu_dereference() around ->real_parent usage [S390] fix cputime overflow in uptime_proc_show [S390] cputime: add sparse checking and cleanup sched: Mark parent and real_parent as __rcu sched, nohz: Fix missing RCU read lock sched, nohz: Set the NOHZ_BALANCE_KICK flag for idle load balancer sched, nohz: Fix the idle cpu check in nohz_idle_balance sched: Use jump_labels for sched_feat sched/accounting: Fix parameter passing in task_group_account_field sched/accounting: Fix user/system tick double accounting sched/accounting: Re-use scheduler statistics for the root cgroup ... Fix up conflicts in - arch/ia64/include/asm/cputime.h, include/asm-generic/cputime.h usecs_to_cputime64() vs the sparse cleanups - kernel/sched/fair.c, kernel/time/tick-sched.c scheduler changes in multiple branches
2012-01-06Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits) cpu: Export cpu_up() rcu: Apply ACCESS_ONCE() to rcu_boost() return value Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" docs: Additional LWN links to RCU API rcu: Augment rcu_batch_end tracing for idle and callback state rcu: Add rcutorture tests for srcu_read_lock_raw() rcu: Make rcutorture test for hotpluggability before offlining CPUs driver-core/cpu: Expose hotpluggability to the rest of the kernel rcu: Remove redundant rcu_cpu_stall_suppress declaration rcu: Adaptive dyntick-idle preparation rcu: Keep invoking callbacks if CPU otherwise idle rcu: Irq nesting is always 0 on rcu_enter_idle_common rcu: Don't check irq nesting from rcu idle entry/exit rcu: Permit dyntick-idle with callbacks pending rcu: Document same-context read-side constraints rcu: Identify dyntick-idle CPUs on first force_quiescent_state() pass rcu: Remove dynticks false positives and RCU failures rcu: Reduce latency of rcu_prepare_for_idle() rcu: Eliminate RCU_FAST_NO_HZ grace-period hang rcu: Avoid needlessly IPIing CPUs at GP end ...
2011-12-23sched/tracing: Add a new tracepoint for sleeptimeArun Sharma
If CONFIG_SCHEDSTATS is defined, the kernel maintains information about how long the task was sleeping or in the case of iowait, blocking in the kernel before getting woken up. This will be useful for sleep time profiling. Note: this information is only provided for sched_fair. Other scheduling classes may choose to provide this in the future. Note: the delay includes the time spent on the runqueue as well. Signed-off-by: Arun Sharma <asharma@fb.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Andrew Vagin <avagin@openvz.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/r/1324512940-32060-2-git-send-email-asharma@fb.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-18ext4: do not reference pa_inode from group_paYongqiang Yang
pa_inode in group_pa is set NULL in ext4_mb_new_group_pa, so pa_inode should be not referenced. Reported-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-12-18writeback: dirty ratelimit - think time compensationWu Fengguang
Compensate the task's think time when computing the final pause time, so that ->dirty_ratelimit can be executed accurately. think time := time spend outside of balance_dirty_pages() In the rare case that the task slept longer than the 200ms period time (result in negative pause time), the sleep time will be compensated in the following periods, too, if it's less than 1 second. Accumulated errors are carefully avoided as long as the max pause area is not hitted. Pseudo code: period = pages_dirtied / task_ratelimit; think = jiffies - dirty_paused_when; pause = period - think; 1) normal case: period > think pause = period - think dirty_paused_when = jiffies + pause nr_dirtied = 0 period time |===============================>| think time pause time |===============>|==============>| ------|----------------|---------------|------------------------ dirty_paused_when jiffies 2) no pause case: period <= think don't pause; reduce future pause time by: dirty_paused_when += period nr_dirtied = 0 period time |===============================>| think time |===================================================>| ------|--------------------------------+-------------------|---- dirty_paused_when jiffies Acked-by: Jan Kara <jack@suse.cz> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-12-18writeback: show writeback reason with __print_symbolicWu Fengguang
This makes the binary trace understandable by trace-cmd. CC: Dave Chinner <david@fromorbit.com> CC: Curt Wohlgemuth <curtw@google.com> CC: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-12-11rcu: Augment rcu_batch_end tracing for idle and callback statePaul E. McKenney
The current rcu_batch_end event trace records only the name of the RCU flavor and the total number of callbacks that remain queued on the current CPU. This is insufficient for testing and tuning the new dyntick-idle RCU_FAST_NO_HZ code, so this commit adds idle state along with whether or not any of the callbacks that were ready to invoke at the beginning of rcu_do_batch() are still queued. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Permit dyntick-idle with callbacks pendingPaul E. McKenney
The current implementation of RCU_FAST_NO_HZ prevents CPUs from entering dyntick-idle state if they have RCU callbacks pending. Unfortunately, this has the side-effect of often preventing them from entering this state, especially if at least one other CPU is not in dyntick-idle state. However, the resulting per-tick wakeup is wasteful in many cases: if the CPU has already fully responded to the current RCU grace period, there will be nothing for it to do until this grace period ends, which will frequently take several jiffies. This commit therefore permits a CPU that has done everything that the current grace period has asked of it (rcu_pending() == 0) even if it still as RCU callbacks pending. However, such a CPU posts a timer to wake it up several jiffies later (6 jiffies, based on experience with grace-period lengths). This wakeup is required to handle situations that can result in all CPUs being in dyntick-idle mode, thus failing to ever complete the current grace period. If a CPU wakes up before the timer goes off, then it cancels that timer, thus avoiding spurious wakeups. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Eliminate RCU_FAST_NO_HZ grace-period hangPaul E. McKenney
With the new implementation of RCU_FAST_NO_HZ, it was possible to hang RCU grace periods as follows: o CPU 0 attempts to go idle, cycles several times through the rcu_prepare_for_idle() loop, then goes dyntick-idle when RCU needs nothing more from it, while still having at least on RCU callback pending. o CPU 1 goes idle with no callbacks. Both CPUs can then stay in dyntick-idle mode indefinitely, preventing the RCU grace period from ever completing, possibly hanging the system. This commit therefore prevents CPUs that have RCU callbacks from entering dyntick-idle mode. This approach also eliminates the need for the end-of-grace-period IPIs used previously. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Add tracing for RCU_FAST_NO_HZPaul E. McKenney
This commit adds trace_rcu_prep_idle(), which is invoked from rcu_prepare_for_idle() and rcu_wake_cpu() to trace attempts on the part of RCU to force CPUs into dyntick-idle mode. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Update trace_rcu_dyntick() header commentPaul E. McKenney
This commit updates the trace_rcu_dyntick() header comment to reflect events added by commit 4b4f421. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Deconfuse dynticks entry-exit tracingPaul E. McKenney
The trace_rcu_dyntick() trace event did not print both the old and the new value of the nesting level, and furthermore printed only the low-order 32 bits of it. This could result in some confusion when interpreting trace-event dumps, so this commit prints both the old and the new value, prints the full 64 bits, and also selects the process-entry/exit increment to print nicely in hexadecimal. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2011-12-11rcu: Add failure tracing to rcutorturePaul E. McKenney
Trace the rcutorture RCU accesses and dump the trace buffer when the first failure is detected. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2011-12-11rcu: Track idleness independent of idle tasksPaul E. McKenney
Earlier versions of RCU used the scheduling-clock tick to detect idleness by checking for the idle task, but handled idleness differently for CONFIG_NO_HZ=y. But there are now a number of uses of RCU read-side critical sections in the idle task, for example, for tracing. A more fine-grained detection of idleness is therefore required. This commit presses the old dyntick-idle code into full-time service, so that rcu_idle_enter(), previously known as rcu_enter_nohz(), is always invoked at the beginning of an idle loop iteration. Similarly, rcu_idle_exit(), previously known as rcu_exit_nohz(), is always invoked at the end of an idle-loop iteration. This allows the idle task to use RCU everywhere except between consecutive rcu_idle_enter() and rcu_idle_exit() calls, in turn allowing architecture maintainers to specify exactly where in the idle loop that RCU may be used. Because some of the userspace upcall uses can result in what looks to RCU like half of an interrupt, it is not possible to expect that the irq_enter() and irq_exit() hooks will give exact counts. This patch therefore expands the ->dynticks_nesting counter to 64 bits and uses two separate bitfields to count process/idle transitions and interrupt entry/exit transitions. It is presumed that userspace upcalls do not happen in the idle loop or from usermode execution (though usermode might do a system call that results in an upcall). The counter is hard-reset on each process/idle transition, which avoids the interrupt entry/exit error from accumulating. Overflow is avoided by the 64-bitness of the ->dyntick_nesting counter. This commit also adds warnings if a non-idle task asks RCU to enter idle state (and these checks will need some adjustment before applying Frederic's OS-jitter patches (http://lkml.org/lkml/2011/10/7/246). In addition, validation of ->dynticks and ->dynticks_nesting is added. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2011-12-06events, sched: Add tracepoint for accounting blocked timeAndrew Vagin
This tracepoint shows how long a task is sleeping in uninterruptible state. E.g. it may show how long and where a mutex is waited for. Signed-off-by: Andrew Vagin <avagin@openvz.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1322471015-107825-8-git-send-email-avagin@openvz.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-11-30regmap: Add trace event for successful cache readsMark Brown
Currently we only trace physical reads, there's no instrumentation if the read is satisfied from cache. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
2011-11-06Merge branch 'modsplit-Oct31_2011' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux * 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits) Revert "tracing: Include module.h in define_trace.h" irq: don't put module.h into irq.h for tracking irqgen modules. bluetooth: macroize two small inlines to avoid module.h ip_vs.h: fix implicit use of module_get/module_put from module.h nf_conntrack.h: fix up fallout from implicit moduleparam.h presence include: replace linux/module.h with "struct module" wherever possible include: convert various register fcns to macros to avoid include chaining crypto.h: remove unused crypto_tfm_alg_modname() inline uwb.h: fix implicit use of asm/page.h for PAGE_SIZE pm_runtime.h: explicitly requires notifier.h linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h miscdevice.h: fix up implicit use of lists and types stop_machine.h: fix implicit use of smp.h for smp_processor_id of: fix implicit use of errno.h in include/linux/of.h of_platform.h: delete needless include <linux/module.h> acpi: remove module.h include from platform/aclinux.h miscdevice.h: delete unnecessary inclusion of module.h device_cgroup.h: delete needless include <linux/module.h> net: sch_generic remove redundant use of <linux/module.h> net: inet_timewait_sock doesnt need <linux/module.h> ... Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in - drivers/media/dvb/frontends/dibx000_common.c - drivers/media/video/{mt9m111.c,ov6650.c} - drivers/mfd/ab3550-core.c - include/linux/dmaengine.h
2011-11-06Merge branch 'writeback-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux * 'writeback-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Add a 'reason' to wb_writeback_work writeback: send work item to queue_io, move_expired_inodes writeback: trace event balance_dirty_pages writeback: trace event bdi_dirty_ratelimit writeback: fix ppc compile warnings on do_div(long long, unsigned long) writeback: per-bdi background threshold writeback: dirty position control - bdi reserve area writeback: control dirty pause time writeback: limit max dirty pause time writeback: IO-less balance_dirty_pages() writeback: per task dirty rate limit writeback: stabilize bdi->dirty_ratelimit writeback: dirty rate control writeback: add bg_threshold parameter to __bdi_update_bandwidth() writeback: dirty position control writeback: account per-bdi accumulated dirtied pages
2011-11-02Merge branch 'for_linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 * 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (97 commits) jbd2: Unify log messages in jbd2 code jbd/jbd2: validate sb->s_first in journal_get_superblock() ext4: let ext4_ext_rm_leaf work with EXT_DEBUG defined ext4: fix a syntax error in ext4_ext_insert_extent when debugging enabled ext4: fix a typo in struct ext4_allocation_context ext4: Don't normalize an falloc request if it can fit in 1 extent. ext4: remove comments about extent mount option in ext4_new_inode() ext4: let ext4_discard_partial_buffers handle unaligned range correctly ext4: return ENOMEM if find_or_create_pages fails ext4: move vars to local scope in ext4_discard_partial_page_buffers_no_lock() ext4: Create helper function for EXT4_IO_END_UNWRITTEN and i_aiodio_unwritten ext4: optimize locking for end_io extent conversion ext4: remove unnecessary call to waitqueue_active() ext4: Use correct locking for ext4_end_io_nolock() ext4: fix race in xattr block allocation path ext4: trace punch_hole correctly in ext4_ext_map_blocks ext4: clean up AGGRESSIVE_TEST code ext4: move variables to their scope ext4: fix quota accounting during migration ext4: migrate cleanup ...
2011-10-31mm: change isolate mode from #define to bitwise typeMinchan Kim
Change ISOLATE_XXX macro with bitwise isolate_mode_t type. Normally, macro isn't recommended as it's type-unsafe and making debugging harder as symbol cannot be passed throught to the debugger. Quote from Johannes " Hmm, it would probably be cleaner to fully convert the isolation mode into independent flags. INACTIVE, ACTIVE, BOTH is currently a tri-state among flags, which is a bit ugly." This patch moves isolate mode from swap.h to mmzone.h by memcontrol.h Signed-off-by: Minchan Kim <minchan.kim@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-10-31Revert "tracing: Include module.h in define_trace.h"Paul Gortmaker
This reverts commit 3a9f987b3141f086de27832514aad9f50a53f754. With all the files that are real modules now having module.h explicitly called out for inclusion, and no reliance on any implicit presence of module.h assumed, we should no longer need this workaround. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-10-31include: replace linux/module.h with "struct module" wherever possiblePaul Gortmaker
The <linux/module.h> pretty much brings in the kitchen sink along with it, so it should be avoided wherever reasonably possible in terms of being included from other commonly used <linux/something.h> files, as it results in a measureable increase on compile times. The worst culprit was probably device.h since it is used everywhere. This file also had an implicit dependency/usage of mutex.h which was masked by module.h, and is also fixed here at the same time. There are over a dozen other headers that simply declare the struct instead of pulling in the whole file, so follow their lead and simply make it a few more. Most of the implicit dependencies on module.h being present by these headers pulling it in have been now weeded out, so we can finally make this change with hopefully minimal breakage. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-10-31writeback: Add a 'reason' to wb_writeback_workCurt Wohlgemuth
This creates a new 'reason' field in a wb_writeback_work structure, which unambiguously identifies who initiates writeback activity. A 'wb_reason' enumeration has been added to writeback.h, to enumerate the possible reasons. The 'writeback_work_class' and tracepoint event class and 'writeback_queue_io' tracepoints are updated to include the symbolic 'reason' in all trace events. And the 'writeback_inodes_sbXXX' family of routines has had a wb_stats parameter added to them, so callers can specify why writeback is being started. Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Curt Wohlgemuth <curtw@google.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-10-31writeback: send work item to queue_io, move_expired_inodesCurt Wohlgemuth
Instead of sending ->older_than_this to queue_io() and move_expired_inodes(), send the entire wb_writeback_work structure. There are other fields of a work item that are useful in these routines and in tracepoints. Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Curt Wohlgemuth <curtw@google.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-10-31writeback: trace event balance_dirty_pagesWu Fengguang
Useful for analyzing the dynamics of the throttling algorithms and debugging user reported problems. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-10-31writeback: trace event bdi_dirty_ratelimitWu Fengguang
It helps understand how various throttle bandwidths are updated. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2011-10-28Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: (549 commits) ALSA: hda - Fix ADC input-amp handling for Cx20549 codec ALSA: hda - Keep EAPD turned on for old Conexant chips ALSA: hda/realtek - Fix missing volume controls with ALC260 ASoC: wm8940: Properly set codec->dapm.bias_level ALSA: hda - Fix pin-config for ASUS W90V ALSA: hda - Fix surround/CLFE headphone and speaker pins order ALSA: hda - Fix typo ALSA: Update the sound git tree URL ALSA: HDA: Add new revision for ALC662 ASoC: max98095: Convert codec->hw_write to snd_soc_write ASoC: keep pointer to resource so it can be freed ASoC: sgtl5000: Fix wrong mask in some snd_soc_update_bits calls ASoC: wm8996: Fix wrong mask for setting WM8996_AIF_CLOCKING_2 ASoC: da7210: Add support for line out and DAC ASoC: da7210: Add support for DAPM ALSA: hda/realtek - Fix DAC assignments of multiple speakers ASoC: Use SGTL5000_LINREG_VDDD_MASK instead of hardcoded mask value ASoC: Set sgtl5000->ldo in ldo_regulator_register ASoC: wm8996: Use SND_SOC_DAPM_AIF_OUT for AIF2 Capture ASoC: wm8994: Use SND_SOC_DAPM_AIF_OUT for AIF3 Capture ...
2011-10-27ext4: optimize ext4_ext_convert_to_initialized()Eric Gouriou
This patch introduces a fast path in ext4_ext_convert_to_initialized() for the case when the conversion can be performed by transferring the newly initialized blocks from the uninitialized extent into an adjacent initialized extent. Doing so removes the expensive invocations of memmove() which occur during extent insertion and the subsequent merge. In practice this should be the common case for clients performing append writes into files pre-allocated via fallocate(FALLOC_FL_KEEP_SIZE). In such a workload performed via direct IO and when using a suboptimal implementation of memmove() (x86_64 prior to the 2.6.39 rewrite), this patch reduces kernel CPU consumption by 32%. Two new trace points are added to ext4_ext_convert_to_initialized() to offer visibility into its operations. No exit trace point has been added due to the multiplicity of return points. This can be revisited once the upstream cleanup is backported. Signed-off-by: Eric Gouriou <egouriou@google.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-10-26Merge branch 'sched-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits) llist: Add back llist_add_batch() and llist_del_first() prototypes sched: Don't use tasklist_lock for debug prints sched: Warn on rt throttling sched: Unify the ->cpus_allowed mask copy sched: Wrap scheduler p->cpus_allowed access sched: Request for idle balance during nohz idle load balance sched: Use resched IPI to kick off the nohz idle balance sched: Fix idle_cpu() llist: Remove cpu_relax() usage in cmpxchg loops sched: Convert to struct llist llist: Add llist_next() irq_work: Use llist in the struct irq_work logic llist: Return whether list is empty before adding in llist_add() llist: Move cpu_relax() to after the cmpxchg() llist: Remove the platform-dependent NMI checks llist: Make some llist functions inline sched, tracing: Show PREEMPT_ACTIVE state in trace_sched_switch sched: Remove redundant test in check_preempt_tick() sched: Add documentation for bandwidth control sched: Return unused runtime on group dequeue ...
2011-10-26Merge branch 'perf-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (121 commits) perf symbols: Increase symbol KSYM_NAME_LEN size perf hists browser: Refuse 'a' hotkey on non symbolic views perf ui browser: Use libslang to read keys perf tools: Fix tracing info recording perf hists browser: Elide DSO column when it is set to just one DSO, ditto for threads perf hists: Don't consider filtered entries when calculating column widths perf hists: Don't decay total_period for filtered entries perf hists browser: Honour symbol_conf.show_{nr_samples,total_period} perf hists browser: Do not exit on tab key with single event perf annotate browser: Don't change selection line when returning from callq perf tools: handle endianness of feature bitmap perf tools: Add prelink suggestion to dso update message perf script: Fix unknown feature comment perf hists browser: Apply the dso and thread filters when merging new batches perf hists: Move the dso and thread filters from hist_browser perf ui browser: Honour the xterm colors perf top tui: Give color hints just on the percentage, like on --stdio perf ui browser: Make the colors configurable and change the defaults perf tui: Remove unneeded call to newtCls on startup perf hists: Don't format the percentage on hist_entry__snprintf ... Fix up conflicts in arch/x86/kernel/kprobes.c manually. Ingo's tree did the insane "add volatile to const array", which just doesn't make sense ("volatile const"?). But we could remove the const *and* make the array volatile to make doubly sure that gcc doesn't optimize it away.. Also fix up kernel/trace/ring_buffer.c non-data-conflicts manually: the reader_lock has been turned into a raw lock by the core locking merge, and there was a new user of it introduced in this perf core merge. Make sure that new use also uses the raw accessor functions.
2011-10-26Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits) rcu: Move propagation of ->completed from rcu_start_gp() to rcu_report_qs_rsp() rcu: Remove rcu_needs_cpu_flush() to avoid false quiescent states rcu: Wire up RCU_BOOST_PRIO for rcutree rcu: Make rcu_torture_boost() exit loops at end of test rcu: Make rcu_torture_fqs() exit loops at end of test rcu: Permit rt_mutex_unlock() with irqs disabled rcu: Avoid having just-onlined CPU resched itself when RCU is idle rcu: Suppress NMI backtraces when stall ends before dump rcu: Prohibit grace periods during early boot rcu: Simplify unboosting checks rcu: Prevent early boot set_need_resched() from __rcu_pending() rcu: Dump local stack if cannot dump all CPUs' stacks rcu: Move __rcu_read_unlock()'s barrier() within if-statement rcu: Improve rcu_assign_pointer() and RCU_INIT_POINTER() documentation rcu: Make rcu_assign_pointer() unconditionally insert a memory barrier rcu: Make rcu_implicit_dynticks_qs() locals be correct size rcu: Eliminate in_irq() checks in rcu_enter_nohz() nohz: Remove nohz_cpu_mask rcu: Document interpretation of RCU-lockdep splats rcu: Allow rcutorture's stat_interval parameter to be changed at runtime ...
2011-10-26Merge branch 'for-linus' of git://github.com/ericvh/linuxLinus Torvalds
* 'for-linus' of git://github.com/ericvh/linux: 9p: fix 9p.txt to advertise msize instead of maxdata net/9p: Convert net/9p protocol dumps to tracepoints fs/9p: change an int to unsigned int fs/9p: Cleanup option parsing in 9p 9p: move dereference after NULL check fs/9p: inode file operation is properly initialized init_special_inode fs/9p: Update zero-copy implementation in 9p
2011-10-25Merge branch 'pm-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm * 'pm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (63 commits) PM / Clocks: Remove redundant NULL checks before kfree() PM / Documentation: Update docs about suspend and CPU hotplug ACPI / PM: Add Sony VGN-FW21E to nonvs blacklist. ARM: mach-shmobile: sh7372 A4R support (v4) ARM: mach-shmobile: sh7372 A3SP support (v4) PM / Sleep: Mark devices involved in wakeup signaling during suspend PM / Hibernate: Improve performance of LZO/plain hibernation, checksum image PM / Hibernate: Do not initialize static and extern variables to 0 PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too PM / Hibernate: Add resumedelay kernel param in addition to resumewait MAINTAINERS: Update linux-pm list address PM / ACPI: Blacklist Vaio VGN-FW520F machine known to require acpi_sleep=nonvs PM / ACPI: Blacklist Sony Vaio known to require acpi_sleep=nonvs PM / Hibernate: Add resumewait param to support MMC-like devices as resume file PM / Hibernate: Fix typo in a kerneldoc comment PM / Hibernate: Freeze kernel threads after preallocating memory PM: Update the policy on default wakeup settings PM / VT: Cleanup #if defined uglyness and fix compile error PM / Suspend: Off by one in pm_suspend() PM / Hibernate: Include storage keys in hibernation image on s390 ...
2011-10-25Merge branch 'for-linus' of git://opensource.wolfsonmicro.com/regmapLinus Torvalds
* 'for-linus' of git://opensource.wolfsonmicro.com/regmap: (62 commits) mfd: Enable rbtree cache for wm831x devices regmap: Support some block operations on cached devices regmap: Allow caches for devices with no defaults regmap: Ensure rbtree syncs registers set to zero properly regmap: Allow rbtree to cache zero default values regmap: Warn on raw I/O as well as bulk reads that bypass cache regmap: Return a sensible error code if we fail to read the cache regmap: Use bsearch() to search the register defaults regmap: Fix doc comment regmap: Optimize the lookup path to use binary search regmap: Ensure we scream if we enable cache bypass/only at the same time regmap: Implement regcache_cache_bypass helper function regmap: Save/restore the bypass state upon syncing regmap: Lock the sync path, ensure we use the lockless _regmap_write() regmap: Fix apostrophe usage regmap: Make _regmap_write() global regmap: Fix lock used for regcache_cache_only() regmap: Grab the lock in regcache_cache_only() regmap: Modify map->cache_bypass directly regmap: Fix regcache_sync generic implementation ...
2011-10-24net/9p: Convert net/9p protocol dumps to tracepointsAneesh Kumar K.V
This helps in more control over debugging. root@qemu-img-64:~# ls /pass/123 ls: cannot access /pass/123: No such file or directory root@qemu-img-64:~# cat /sys/kernel/debug/tracing/trace # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | ls-1536 [001] 70.928584: 9p_protocol_dump: clnt 18446612132784021504 P9_TWALK(tag = 1) 000: 16 00 00 00 6e 01 00 01 00 00 00 02 00 00 00 01 010: 00 03 00 31 32 33 00 00 00 ff ff ff ff 00 00 00 ls-1536 [001] 70.928587: <stack trace> => trace_9p_protocol_dump => p9pdu_finalize => p9_client_rpc => p9_client_walk => v9fs_vfs_lookup => d_alloc_and_lookup => walk_component => path_lookupat ls-1536 [000] 70.929696: 9p_protocol_dump: clnt 18446612132784021504 P9_RLERROR(tag = 1) 000: 0b 00 00 00 07 01 00 02 00 00 00 4e 03 00 02 00 010: 00 00 00 00 03 00 02 00 00 00 00 00 ff 43 00 00 ls-1536 [000] 70.929697: <stack trace> => trace_9p_protocol_dump => p9_client_rpc => p9_client_walk => v9fs_vfs_lookup => d_alloc_and_lookup => walk_component => path_lookupat => do_path_lookup Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2011-10-07Merge branch 'pm-runtime' into pm-for-linusRafael J. Wysocki
* pm-runtime: PM / Tracing: build rpm-traces.c only if CONFIG_PM_RUNTIME is set PM / Runtime: Replace dev_dbg() with trace_rpm_*() PM / Runtime: Introduce trace points for tracing rpm_* functions PM / Runtime: Don't run callbacks under lock for power.irq_safe set USB: Add wakeup info to debugging messages PM / Runtime: pm_runtime_idle() can be called in atomic context PM / Runtime: Add macro to test for runtime PM events PM / Runtime: Add might_sleep() to runtime PM functions
2011-10-06Merge commit 'v3.1-rc9' into perf/coreIngo Molnar
Merge reason: pick up latest fixes. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-10-04Merge branch 'linus' into sched/coreIngo Molnar
Merge reason: pick up the latest fixes. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-10-04perf: Fix counter of ftrace eventsAndrew Vagin
Each event adds some points to its counters. By default it adds 1, and a number of points may be transmited in event's parameters. E.g. sched:sched_stat_runtime adds how long process has been running. But this functionality was broken by v2.6.31-rc5-392-gf413cdb and now the event's parameters doesn't affect on a number of points. TP_perf_assign isn't defined, so __perf_count(c) isn't executed and __count is always equal to 1. Signed-off-by: Andrew Vagin <avagin@openvz.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1317052535-1765247-2-git-send-email-avagin@openvz.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-10-03writeback: IO-less balance_dirty_pages()Wu Fengguang
As proposed by Chris, Dave and Jan, don't start foreground writeback IO inside balance_dirty_pages(). Instead, simply let it idle sleep for some time to throttle the dirtying task. In the mean while, kick off the per-bdi flusher thread to do background writeback IO. RATIONALS ========= - disk seeks on concurrent writeback of multiple inodes (Dave Chinner) If every thread doing writes and being throttled start foreground writeback, it leads to N IO submitters from at least N different inodes at the same time, end up with N different sets of IO being issued with potentially zero locality to each other, resulting in much lower elevator sort/merge efficiency and hence we seek the disk all over the place to service the different sets of IO. OTOH, if there is only one submission thread, it doesn't jump between inodes in the same way when congestion clears - it keeps writing to the same inode, resulting in large related chunks of sequential IOs being issued to the disk. This is more efficient than the above foreground writeback because the elevator works better and the disk seeks less. - lock contention and cache bouncing on concurrent IO submitters (Dave Chinner) With this patchset, the fs_mark benchmark on a 12-drive software RAID0 goes from CPU bound to IO bound, freeing "3-4 CPUs worth of spinlock contention". * "CPU usage has dropped by ~55%", "it certainly appears that most of the CPU time saving comes from the removal of contention on the inode_wb_list_lock" (IMHO at least 10% comes from the reduction of cacheline bouncing, because the new code is able to call much less frequently into balance_dirty_pages() and hence access the global page states) * the user space "App overhead" is reduced by 20%, by avoiding the cacheline pollution by the complex writeback code path * "for a ~5% throughput reduction", "the number of write IOs have dropped by ~25%", and the elapsed time reduced from 41:42.17 to 40:53.23. * On a simple test of 100 dd, it reduces the CPU %system time from 30% to 3%, and improves IO throughput from 38MB/s to 42MB/s. - IO size too small for fast arrays and too large for slow USB sticks The write_chunk used by current balance_dirty_pages() cannot be directly set to some large value (eg. 128MB) for better IO efficiency. Because it could lead to more than 1 second user perceivable stalls. Even the current 4MB write size may be too large for slow USB sticks. The fact that balance_dirty_pages() starts IO on itself couples the IO size to wait time, which makes it hard to do suitable IO size while keeping the wait time under control. Now it's possible to increase writeback chunk size proportional to the disk bandwidth. In a simple test of 50 dd's on XFS, 1-HDD, 3GB ram, the larger writeback size dramatically reduces the seek count to 1/10 (far beyond my expectation) and improves the write throughput by 24%. - long block time in balance_dirty_pages() hurts desktop responsiveness Many of us may have the experience: it often takes a couple of seconds or even long time to stop a heavy writing dd/cp/tar command with Ctrl-C or "kill -9". - IO pipeline broken by bumpy write() progress There are a broad class of "loop {read(buf); write(buf);}" applications whose read() pipeline will be under-utilized or even come to a stop if the write()s have long latencies _or_ don't progress in a constant rate. The current threshold based throttling inherently transfers the large low level IO completion fluctuations to bumpy application write()s, and further deteriorates with increasing number of dirtiers and/or bdi's. For example, when doing 50 dd's + 1 remote rsync to an XFS partition, the rsync progresses very bumpy in legacy kernel, and throughput is improved by 67% by this patchset. (plus the larger write chunk size, it will be 93% speedup). The new rate based throttling can support 1000+ dd's with excellent smoothness, low latency and low overheads. For the above reasons, it's much better to do IO-less and low latency pauses in balance_dirty_pages(). Jan Kara, Dave Chinner and me explored the scheme to let balance_dirty_pages() wait for enough writeback IO completions to safeguard the dirty limit. However it's found to have two problems: - in large NUMA systems, the per-cpu counters may have big accounting errors, leading to big throttle wait time and jitters. - NFS may kill large amount of unstable pages with one single COMMIT. Because NFS server serves COMMIT with expensive fsync() IOs, it is desirable to delay and reduce the number of COMMITs. So it's not likely to optimize away such kind of bursty IO completions, and the resulted large (and tiny) stall times in IO completion based throttling. So here is a pause time oriented approach, which tries to control the pause time in each balance_dirty_pages() invocations, by controlling the number of pages dirtied before calling balance_dirty_pages(), for smooth and efficient dirty throttling: - avoid useless (eg. zero pause time) balance_dirty_pages() calls - avoid too small pause time (less than 4ms, which burns CPU power) - avoid too large pause time (more than 200ms, which hurts responsiveness) - avoid big fluctuations of pause times It can control pause times at will. The default policy (in a followup patch) will be to do ~10ms pauses in 1-dd case, and increase to ~100ms in 1000-dd case. BEHAVIOR CHANGE =============== (1) dirty threshold Users will notice that the applications will get throttled once crossing the global (background + dirty)/2=15% threshold, and then balanced around 17.5%. Before patch, the behavior is to just throttle it at 20% dirtyable memory in 1-dd case. Since the task will be soft throttled earlier than before, it may be perceived by end users as performance "slow down" if his application happens to dirty more than 15% dirtyable memory. (2) smoothness/responsiveness Users will notice a more responsive system during heavy writeback. "killall dd" will take effect instantly. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>