test/test_sref_weakref: new test module

3 files changed, 129 insertions, 4 deletions

diff --git a/Makefrag.am b/Makefrag.am
index b0a5d32b..4ac5cef1 100644
--- a/Makefrag.am
+++ b/Makefrag.am
@@ -90,14 +90,18 @@ if TEST_SREF_DIRTY_ZEROES
 x15_SOURCES += test/test_sref_dirty_zeroes.c
 endif TEST_SREF_DIRTY_ZEROES
 
-if TEST_VM_PAGE_FILL
-x15_SOURCES += test/test_vm_page_fill.c
-endif TEST_VM_PAGE_FILL
-
 if TEST_SREF_NOREF
 x15_SOURCES += test/test_sref_noref.c
 endif TEST_SREF_NOREF
 
+if TEST_SREF_WEAKREF
+x15_SOURCES += test/test_sref_weakref.c
+endif TEST_SREF_WEAKREF
+
+if TEST_VM_PAGE_FILL
+x15_SOURCES += test/test_vm_page_fill.c
+endif TEST_VM_PAGE_FILL
+
 if TEST_X86_DOUBLE_FAULT
 x15_SOURCES += test/test_x86_double_fault.c
 endif TEST_X86_DOUBLE_FAULT
diff --git a/configure.ac b/configure.ac
index 9c130ed6..023140bd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,6 +43,7 @@ m4_define([ENABLE_TEST_MODULE],
                    [pmap_update_mp], [test_pmap_update_mp=yes],
                    [sref_dirty_zeroes], [test_sref_dirty_zeroes=yes],
                    [sref_noref], [test_sref_noref=yes],
+                   [sref_weakref], [test_sref_weakref=yes],
                    [vm_page_fill], [test_vm_page_fill=yes],
                    [x86_double_fault], [test_x86_double_fault=yes],
                    [xcall], [test_xcall=yes],
@@ -60,6 +61,8 @@ AM_CONDITIONAL([TEST_SREF_DIRTY_ZEROES],
                [test x"$test_sref_dirty_zeroes" = xyes])
 AM_CONDITIONAL([TEST_SREF_NOREF],
                [test x"$test_sref_noref" = xyes])
+AM_CONDITIONAL([TEST_SREF_WEAKREF],
+               [test x"$test_sref_weakref" = xyes])
 AM_CONDITIONAL([TEST_VM_PAGE_FILL],
                [test x"$test_vm_page_fill" = xyes])
 AM_CONDITIONAL([TEST_X86_DOUBLE_FAULT],
diff --git a/test/test_sref_weakref.c b/test/test_sref_weakref.c
new file mode 100644
index 00000000..079eeaf8
--- /dev/null
+++ b/test/test_sref_weakref.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * This module is a stress test of the weak reference implementation
+ * of scalable reference counters. Two threads are created. The first
+ * periodically allocates a page and initializes a counter inside the
+ * page, then immediately decrements the counter. The intended effect
+ * is to mark the counter as dying as soon as possible. The second
+ * thread continually attempts to obtain a reference, i.e. increment
+ * the counter, through a weak reference. Counters are regularly
+ * printed to monitor activity. There should be almost as many noref
+ * calls as there are iterations in the first thread (a bit lower
+ * because of the review delay) and a good amount of revives (at least
+ * on multiprocessor machines) caused by successfully getting the counter
+ * from the weak reference while it is marked dying but still in review.
+ * Iterations in the second thread may spike when obtaining a reference
+ * fails, because the error case is much faster and continues until the
+ * first thread reinitializes the weak reference.
+ */
+
+#include <kern/error.h>
+#include <kern/evcnt.h>
+#include <kern/macros.h>
+#include <kern/sref.h>
+#include <kern/stddef.h>
+#include <kern/thread.h>
+#include <test/test.h>
+#include <vm/vm_kmem.h>
+
+static struct sref_weakref test_weakref;
+
+static void
+test_noref(struct sref_counter *counter)
+{
+    vm_kmem_free(counter, sizeof(*counter));
+}
+
+static void
+test_run(void *arg)
+{
+    struct sref_counter *counter;
+    volatile unsigned long j;
+    unsigned long i;
+
+    (void)arg;
+
+    for (i = 1; /* no condition */; i++) {
+        counter = vm_kmem_alloc(sizeof(*counter));
+
+        if (counter == NULL) {
+            continue;
+        }
+
+        sref_counter_init(counter, &test_weakref, test_noref);
+        sref_counter_dec(counter);
+
+        for (j = 0; j < 0x20000000; j++);
+
+        printk("run: iterations: %lu\n", i);
+        evcnt_info("sref_epoch");
+        evcnt_info("sref_dirty_zero");
+        evcnt_info("sref_revive");
+        evcnt_info("sref_true_zero");
+    }
+}
+
+static void
+test_ref(void *arg)
+{
+    struct sref_counter *counter;
+    unsigned long i;
+
+    (void)arg;
+
+    for (i = 1; /* no condition */; i++) {
+        counter = sref_weakref_get(&test_weakref);
+
+        if (counter != NULL) {
+            sref_counter_dec(counter);
+        }
+
+        if ((i % 10000000) == 0) {
+            printk("ref: iterations: %lu\n", i);
+        }
+    }
+}
+
+void
+test_setup(void)
+{
+    struct thread_attr attr;
+    struct thread *thread;
+    int error;
+
+    thread_attr_init(&attr, THREAD_KERNEL_PREFIX "test_run");
+    thread_attr_set_detached(&attr);
+    error = thread_create(&thread, &attr, test_run, NULL);
+    error_check(error, "thread_create");
+
+    thread_attr_init(&attr, THREAD_KERNEL_PREFIX "test_ref");
+    thread_attr_set_detached(&attr);
+    error = thread_create(&thread, &attr, test_ref, NULL);
+    error_check(error, "thread_create");
+}