[PATCH] sleep profiling
Implement prof=sleep profiling. TASK_UNINTERRUPTIBLE sleeps will be taken
as a profile hit, and every millisecond spent sleeping causes a profile-hit
for the call site that initiated the sleep.
Sample readprofile output on i386:
306 ps2_sendbyte 1.3973
432 call_usermodehelper_keys 1.9548
484 ps2_command 0.6453
790 __driver_attach 4.7879
1593 msleep 44.2500
3976 sync_buffer 64.1290
4076 do_lookup 12.4648
8587 sync_page 122.6714
20820 total 0.0067
(NOTE: architectures need to check whether get_wchan() can be called from
deep within the wakeup path.)
akpm: we need to mark more functions __sched. lock_sock(), msleep(), others..
akpm: the contention in do_lookup() is a surprise. Presumably doing disk
reads for directory contents while holding i_mutex.
[akpm@osdl.org: various fixes]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/profile.c b/kernel/profile.c
index 15b012df..04fd84e 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -40,7 +40,7 @@
static atomic_t *prof_buffer;
static unsigned long prof_len, prof_shift;
-static int prof_on __read_mostly;
+int prof_on __read_mostly;
static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
@@ -51,9 +51,19 @@
static int __init profile_setup(char * str)
{
static char __initdata schedstr[] = "schedule";
+ static char __initdata sleepstr[] = "sleep";
int par;
- if (!strncmp(str, schedstr, strlen(schedstr))) {
+ if (!strncmp(str, sleepstr, strlen(sleepstr))) {
+ prof_on = SLEEP_PROFILING;
+ if (str[strlen(sleepstr)] == ',')
+ str += strlen(sleepstr) + 1;
+ if (get_option(&str, &par))
+ prof_shift = par;
+ printk(KERN_INFO
+ "kernel sleep profiling enabled (shift: %ld)\n",
+ prof_shift);
+ } else if (!strncmp(str, sleepstr, strlen(sleepstr))) {
prof_on = SCHED_PROFILING;
if (str[strlen(schedstr)] == ',')
str += strlen(schedstr) + 1;
@@ -204,7 +214,8 @@
* positions to which hits are accounted during short intervals (e.g.
* several seconds) is usually very small. Exclusion from buffer
* flipping is provided by interrupt disablement (note that for
- * SCHED_PROFILING profile_hit() may be called from process context).
+ * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
+ * process context).
* The hash function is meant to be lightweight as opposed to strong,
* and was vaguely inspired by ppc64 firmware-supported inverted
* pagetable hash functions, but uses a full hashtable full of finite
@@ -257,7 +268,7 @@
mutex_unlock(&profile_flip_mutex);
}
-void profile_hit(int type, void *__pc)
+void profile_hits(int type, void *__pc, unsigned int nr_hits)
{
unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
int i, j, cpu;
@@ -274,21 +285,31 @@
put_cpu();
return;
}
+ /*
+ * We buffer the global profiler buffer into a per-CPU
+ * queue and thus reduce the number of global (and possibly
+ * NUMA-alien) accesses. The write-queue is self-coalescing:
+ */
local_irq_save(flags);
do {
for (j = 0; j < PROFILE_GRPSZ; ++j) {
if (hits[i + j].pc == pc) {
- hits[i + j].hits++;
+ hits[i + j].hits += nr_hits;
goto out;
} else if (!hits[i + j].hits) {
hits[i + j].pc = pc;
- hits[i + j].hits = 1;
+ hits[i + j].hits = nr_hits;
goto out;
}
}
i = (i + secondary) & (NR_PROFILE_HIT - 1);
} while (i != primary);
- atomic_inc(&prof_buffer[pc]);
+
+ /*
+ * Add the current hit(s) and flush the write-queue out
+ * to the global buffer:
+ */
+ atomic_add(nr_hits, &prof_buffer[pc]);
for (i = 0; i < NR_PROFILE_HIT; ++i) {
atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
hits[i].pc = hits[i].hits = 0;
@@ -356,14 +377,14 @@
#define profile_flip_buffers() do { } while (0)
#define profile_discard_flip_buffers() do { } while (0)
-void profile_hit(int type, void *__pc)
+void profile_hits(int type, void *__pc, unsigned int nr_hits)
{
unsigned long pc;
if (prof_on != type || !prof_buffer)
return;
pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
- atomic_inc(&prof_buffer[min(pc, prof_len - 1)]);
+ atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
}
#endif /* !CONFIG_SMP */