btw., if you run -tip and have these enabled:
CONFIG_PERF_COUNTER=y
CONFIG_EVENT_TRACING=y
cd tools/perf/
make -j install
... then you can use a couple of new perfcounters features to
measure scheduler latencies. For example:
perf stat -e sched:sched_stat_wait -e task-clock ./hackbench 20
Will tell you how many times this workload got delayed by waiting
for CPU time.
You can repeat the workload as well and see the statistical
properties of those metrics:
aldebaran:/home/mingo> perf stat --repeat 10 -e \
sched:sched_stat_wait:r -e task-clock ./hackbench 20
Time: 0.251
Time: 0.214
Time: 0.254
Time: 0.278
Time: 0.245
Time: 0.308
Time: 0.242
Time: 0.222
Time: 0.268
Time: 0.244
Performance counter stats for './hackbench 20' (10 runs):
59826 sched:sched_stat_wait # 0.026 M/sec ( +- 5.540% )
2280.099643 task-clock-msecs # 7.525 CPUs ( +- 1.620% )
0.303013390 seconds time elapsed ( +- 3.189% )
To get scheduling events, do:
# perf list 2>&1 | grep sched:
sched:sched_kthread_stop [Tracepoint event]
sched:sched_kthread_stop_ret [Tracepoint event]
sched:sched_wait_task [Tracepoint event]
sched:sched_wakeup [Tracepoint event]
sched:sched_wakeup_new [Tracepoint event]
sched:sched_switch [Tracepoint event]
sched:sched_migrate_task [Tracepoint event]
sched:sched_process_free [Tracepoint event]
sched:sched_process_exit [Tracepoint event]
sched:sched_process_wait [Tracepoint event]
sched:sched_process_fork [Tracepoint event]
sched:sched_signal_send [Tracepoint event]
sched:sched_stat_wait [Tracepoint event]
sched:sched_stat_sleep [Tracepoint event]
sched:sched_stat_iowait [Tracepoint event]
stat_wait/sleep/iowait would be the interesting ones, for latency
analysis.
Or, if you want to see all the specific delays and want to see
min/max/avg, you can do:
perf record -e sched:sched_stat_wait:r -f -R -c 1 ./hackbench 20
perf trace
Ingo
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DIR *dir = opendir(some_path);
struct dirent *d;
struct dirent d_mem;
while (readdir_r(d, &d_mem, &d) == 0) {
char path[PATH_MAX];
snprintf(path, sizeof(path), "%s/%s/somefile", some_path, d->d_name);
int fd = open(path, O_RDONLY);
if (fd != -1) {
... do something ...
close (fd);
}
}
closedir(dir);
DIR *dir = opendir(some_path);
int dfd = dirfd(dir);
struct dirent64 *d;
while ((d = readdir64(dir)) != NULL) {
if (d->d_type != DT_DIR && d->d_type != DT_UNKNOWN)
continue;
char path[PATH_MAX];
snprintf(path, sizeof(path), "%s/somefile", d->d_name);
int fd = openat(dfd, path, O_RDONLY);
if (fd != -1) {
... do something ...
close (fd);
}
}
closedir(dir);
$ cat /proc/meminfo
MemTotal: 6037184 kB
MemFree: 1229820 kB
Buffers: 252336 kB
Cached: 3673464 kB
SwapCached: 0 kB
Active: 1463432 kB
Inactive: 2772100 kB
Active(anon): 315332 kB
Inactive(anon): 16 kB
Active(file): 1148100 kB
Inactive(file): 2772084 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 10174448 kB
SwapFree: 10174448 kB
Dirty: 1092 kB
Writeback: 0 kB
AnonPages: 309728 kB
Mapped: 75640 kB
Shmem: 5620 kB
Slab: 379376 kB
SReclaimable: 339928 kB
SUnreclaim: 39448 kB
KernelStack: 2392 kB
PageTables: 33848 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 13193040 kB
Committed_AS: 788376 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 46116 kB
VmallocChunk: 34359682980 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 7104 kB
DirectMap2M: 3137536 kB
DirectMap1G: 3145728 kB
Next patсh -
http://www.kernel.org/diff/diffview.cgi?file=%2Fpub%2Flinux%2Fkernel%2F%2Fv2.6%2Fsnapshots%2Fpatch-2.6.31-git2.bz2;z=548
This patch defines the core processes that are working with nice leve equal to
zero , as in the BFS. :)
Why?
VirtualBox, Vmware, QEMU, Firefox, Azureus, and many subsystems and
applications began working with large timeouts. In appearance similar to
hang.
Compare
2.6.31-git2 with KTHREAD_NICE_LEVEL = 0
2.6.31-git2 with KTHREAD_NICE_LEVEL = -5
Diff.
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 5fe7099..eb8751a 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -16,6 +16,8 @@
#include
#include
+#define KTHREAD_NICE_LEVEL (-5)
+
static DEFINE_SPINLOCK(kthread_create_lock);
static LIST_HEAD(kthread_create_list);
struct task_struct *kthreadd_task;
@@ -143,6 +145,7 @@ struct task_struct *kthread_create(int (*threadfn)(void
*data),
* The kernel thread should not inherit these properties.
*/
sched_setscheduler_nocheck(create.result, SCHED_NORMAL,
¶m);
+ set_user_nice(create.result, KTHREAD_NICE_LEVEL);
set_cpus_allowed_ptr(create.result, cpu_all_mask);
}
return create.result;
@@ -218,6 +221,7 @@ int kthreadd(void *unused)
/* Setup a clean context for our children to inherit. */
set_task_comm(tsk, "kthreadd");
ignore_signals(tsk);
+ set_user_nice(tsk, KTHREAD_NICE_LEVEL);
set_cpus_allowed_ptr(tsk, cpu_all_mask);
set_mems_allowed(node_possible_map);
Used benchmarks.
# cyclictest and signaltest -
http://www.osadl.org/Realtime-test-utilities-cyclictest-and-s.rt-test-cyclictest-signaltest.0.html
----------
CYCLE TEST
----------
-T: 0 ( 5263) P: 0 I:1000 C: 98345 Min: 8 Act:656014 Avg:287390 Max:
656450
-T: 1 ( 5264) P: 0 I:1500 C: 65680 Min: 7 Act:481583 Avg:236140 Max:
482343
-T: 2 ( 5265) P: 0 I:2000 C: 49358 Min: 7 Act:286071 Avg:111300 Max:
287453
-T: 3 ( 5266) P: 0 I:2500 C: 39453 Min: 7 Act:370028 Avg:116111 Max:
372481
+T: 0 ( 6634) P: 0 I:1000 C: 98888 Min: 7 Act:113011 Avg:28733 Max:
113817
+T: 1 ( 6635) P: 0 I:1500 C: 65953 Min: 8 Act:72013 Avg:25026 Max:
73110
+T: 2 ( 6636) P: 0 I:2000 C: 49468 Min: 6 Act:66076 Avg:17455 Max:
67486
+T: 3 ( 6637) P: 0 I:2500 C: 39580 Min: 7 Act:52514 Avg:12882 Max:
53256
----------
SIGNAL TEST
----------
-T: 0 ( 5285) P: 0 C: 100000 Min: 13 Act: 23 Avg: 30 Max: 9229
-T: 1 ( 5286) P: 0 C: 100000 Min: 13 Act: 99 Avg: 662 Max: 17282
-T: 2 ( 5287) P: 0 C: 100000 Min: 13 Act: 110 Avg: 662 Max: 17294
-T: 3 ( 5288) P: 0 C: 100000 Min: 13 Act: 119 Avg: 662 Max: 18645
+T: 0 ( 6698) P: 0 C: 100000 Min: 13 Act: 22 Avg: 24 Max: 7898
+T: 1 ( 6699) P: 0 C: 100000 Min: 13 Act: 104 Avg: 654 Max: 15728
+T: 2 ( 6700) P: 0 C: 100000 Min: 13 Act: 114 Avg: 654 Max: 15740
+T: 3 ( 6701) P: 0 C: 100000 Min: 13 Act: 124 Avg: 654 Max: 16102
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