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Subject[PATCH] lockstat: report avg wait and hold times
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While both the nr and total times are showed, having the avg lock hold
and wait times show in the report is quite useful when working on
performance related issues. Furthermore, I find myself constantly
doing the calculations manually.

In addition, some of the documentation examples were changed to easily
update them to show the two new columns. No textual change otherwise,
as descriptions match the lockstat output.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
---
Documentation/lockstat.txt | 123 ++++++++++++++++++++++-----------------------
kernel/lockdep_proc.c | 15 +++---
2 files changed, 70 insertions(+), 68 deletions(-)

diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt
index dd2f7b2..72d0106 100644
--- a/Documentation/lockstat.txt
+++ b/Documentation/lockstat.txt
@@ -46,16 +46,14 @@ With these hooks we provide the following statistics:
contentions - number of lock acquisitions that had to wait
wait time min - shortest (non-0) time we ever had to wait for a lock
max - longest time we ever had to wait for a lock
- total - total time we spend waiting on this lock
+ total - total time we spend waiting on this lock
+ avg - average time spent waiting on this lock
acq-bounces - number of lock acquisitions that involved x-cpu data
acquisitions - number of times we took the lock
hold time min - shortest (non-0) time we ever held the lock
- max - longest time we ever held the lock
- total - total time this lock was held
-
-From these number various other statistics can be derived, such as:
-
- hold time average = hold time total / acquisitions
+ max - longest time we ever held the lock
+ total - total time this lock was held
+ avg - average time this lock was held

These numbers are gathered per lock class, per read/write state (when
applicable).
@@ -84,37 +82,38 @@ Look at the current lock statistics:

# less /proc/lock_stat

-01 lock_stat version 0.3
-02 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-03 class name con-bounces contentions waittime-min waittime-max waittime-total acq-bounces acquisitions holdtime-min holdtime-max holdtime-total
-04 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+01 lock_stat version 0.4
+02-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+03 class name con-bounces contentions waittime-min waittime-max waittime-total waittime-avg acq-bounces acquisitions holdtime-min holdtime-max holdtime-total holdtime-avg
+04-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
05
-06 &mm->mmap_sem-W: 233 538 18446744073708 22924.27 607243.51 1342 45806 1.71 8595.89 1180582.34
-07 &mm->mmap_sem-R: 205 587 18446744073708 28403.36 731975.00 1940 412426 0.58 187825.45 6307502.88
-08 ---------------
-09 &mm->mmap_sem 487 [<ffffffff8053491f>] do_page_fault+0x466/0x928
-10 &mm->mmap_sem 179 [<ffffffff802a6200>] sys_mprotect+0xcd/0x21d
-11 &mm->mmap_sem 279 [<ffffffff80210a57>] sys_mmap+0x75/0xce
-12 &mm->mmap_sem 76 [<ffffffff802a490b>] sys_munmap+0x32/0x59
-13 ---------------
-14 &mm->mmap_sem 270 [<ffffffff80210a57>] sys_mmap+0x75/0xce
-15 &mm->mmap_sem 431 [<ffffffff8053491f>] do_page_fault+0x466/0x928
-16 &mm->mmap_sem 138 [<ffffffff802a490b>] sys_munmap+0x32/0x59
-17 &mm->mmap_sem 145 [<ffffffff802a6200>] sys_mprotect+0xcd/0x21d
+06 &mm->mmap_sem-W: 46 84 0.26 939.10 16371.53 194.90 47291 2922365 0.16 2220301.69 17464026916.32 5975.99
+07 &mm->mmap_sem-R: 37 100 1.31 299502.61 325629.52 3256.30 212344 34316685 0.10 7744.91 95016910.20 2.77
+08 ---------------
+09 &mm->mmap_sem 1 [<ffffffff811502a7>] khugepaged_scan_mm_slot+0x57/0x280
+19 &mm->mmap_sem 96 [<ffffffff815351c4>] __do_page_fault+0x1d4/0x510
+11 &mm->mmap_sem 34 [<ffffffff81113d77>] vm_mmap_pgoff+0x87/0xd0
+12 &mm->mmap_sem 17 [<ffffffff81127e71>] vm_munmap+0x41/0x80
+13 ---------------
+14 &mm->mmap_sem 1 [<ffffffff81046fda>] dup_mmap+0x2a/0x3f0
+15 &mm->mmap_sem 60 [<ffffffff81129e29>] SyS_mprotect+0xe9/0x250
+16 &mm->mmap_sem 41 [<ffffffff815351c4>] __do_page_fault+0x1d4/0x510
+17 &mm->mmap_sem 68 [<ffffffff81113d77>] vm_mmap_pgoff+0x87/0xd0
18
-19 ...............................................................................................................................................................................................
+19.............................................................................................................................................................................................................................
20
-21 dcache_lock: 621 623 0.52 118.26 1053.02 6745 91930 0.29 316.29 118423.41
-22 -----------
-23 dcache_lock 179 [<ffffffff80378274>] _atomic_dec_and_lock+0x34/0x54
-24 dcache_lock 113 [<ffffffff802cc17b>] d_alloc+0x19a/0x1eb
-25 dcache_lock 99 [<ffffffff802ca0dc>] d_rehash+0x1b/0x44
-26 dcache_lock 104 [<ffffffff802cbca0>] d_instantiate+0x36/0x8a
-27 -----------
-28 dcache_lock 192 [<ffffffff80378274>] _atomic_dec_and_lock+0x34/0x54
-29 dcache_lock 98 [<ffffffff802ca0dc>] d_rehash+0x1b/0x44
-30 dcache_lock 72 [<ffffffff802cc17b>] d_alloc+0x19a/0x1eb
-31 dcache_lock 112 [<ffffffff802cbca0>] d_instantiate+0x36/0x8a
+21 unix_table_lock: 110 112 0.21 49.24 163.91 1.46 21094 66312 0.12 624.42 31589.81 0.48
+22 ---------------
+23 unix_table_lock 45 [<ffffffff8150ad8e>] unix_create1+0x16e/0x1b0
+24 unix_table_lock 47 [<ffffffff8150b111>] unix_release_sock+0x31/0x250
+25 unix_table_lock 15 [<ffffffff8150ca37>] unix_find_other+0x117/0x230
+26 unix_table_lock 5 [<ffffffff8150a09f>] unix_autobind+0x11f/0x1b0
+27 ---------------
+28 unix_table_lock 39 [<ffffffff8150b111>] unix_release_sock+0x31/0x250
+29 unix_table_lock 49 [<ffffffff8150ad8e>] unix_create1+0x16e/0x1b0
+30 unix_table_lock 20 [<ffffffff8150ca37>] unix_find_other+0x117/0x230
+31 unix_table_lock 4 [<ffffffff8150a09f>] unix_autobind+0x11f/0x1b0
+

This excerpt shows the first two lock class statistics. Line 01 shows the
output version - each time the format changes this will be updated. Line 02-04
@@ -131,30 +130,30 @@ The integer part of the time values is in us.

Dealing with nested locks, subclasses may appear:

-32...............................................................................................................................................................................................
+32...........................................................................................................................................................................................................................
33
-34 &rq->lock: 13128 13128 0.43 190.53 103881.26 97454 3453404 0.00 401.11 13224683.11
+34 &rq->lock: 13128 13128 0.43 190.53 103881.26 7.91 97454 3453404 0.00 401.11 13224683.11 3.82
35 ---------
-36 &rq->lock 645 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
-37 &rq->lock 297 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
-38 &rq->lock 360 [<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
-39 &rq->lock 428 [<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
+36 &rq->lock 645 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+37 &rq->lock 297 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+38 &rq->lock 360 [<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
+39 &rq->lock 428 [<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
40 ---------
-41 &rq->lock 77 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
-42 &rq->lock 174 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
-43 &rq->lock 4715 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
-44 &rq->lock 893 [<ffffffff81340524>] schedule+0x157/0x7b8
+41 &rq->lock 77 [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+42 &rq->lock 174 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+43 &rq->lock 4715 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+44 &rq->lock 893 [<ffffffff81340524>] schedule+0x157/0x7b8
45
-46...............................................................................................................................................................................................
+46...........................................................................................................................................................................................................................
47
-48 &rq->lock/1: 11526 11488 0.33 388.73 136294.31 21461 38404 0.00 37.93 109388.53
+48 &rq->lock/1: 1526 11488 0.33 388.73 136294.31 11.86 21461 38404 0.00 37.93 109388.53 2.84
49 -----------
-50 &rq->lock/1 11526 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+50 &rq->lock/1 11526 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
51 -----------
-52 &rq->lock/1 5645 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
-53 &rq->lock/1 1224 [<ffffffff81340524>] schedule+0x157/0x7b8
-54 &rq->lock/1 4336 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
-55 &rq->lock/1 181 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+52 &rq->lock/1 5645 [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+53 &rq->lock/1 1224 [<ffffffff81340524>] schedule+0x157/0x7b8
+54 &rq->lock/1 4336 [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+55 &rq->lock/1 181 [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a

Line 48 shows statistics for the second subclass (/1) of &rq->lock class
(subclass starts from 0), since in this case, as line 50 suggests,
@@ -163,16 +162,16 @@ double_rq_lock actually acquires a nested lock of two spinlocks.
View the top contending locks:

# grep : /proc/lock_stat | head
- &inode->i_data.tree_lock-W: 15 21657 0.18 1093295.30 11547131054.85 58 10415 0.16 87.51 6387.60
- &inode->i_data.tree_lock-R: 0 0 0.00 0.00 0.00 23302 231198 0.25 8.45 98023.38
- dcache_lock: 1037 1161 0.38 45.32 774.51 6611 243371 0.15 306.48 77387.24
- &inode->i_mutex: 161 286 18446744073709 62882.54 1244614.55 3653 20598 18446744073709 62318.60 1693822.74
- &zone->lru_lock: 94 94 0.53 7.33 92.10 4366 32690 0.29 59.81 16350.06
- &inode->i_data.i_mmap_mutex: 79 79 0.40 3.77 53.03 11779 87755 0.28 116.93 29898.44
- &q->__queue_lock: 48 50 0.52 31.62 86.31 774 13131 0.17 113.08 12277.52
- &rq->rq_lock_key: 43 47 0.74 68.50 170.63 3706 33929 0.22 107.99 17460.62
- &rq->rq_lock_key#2: 39 46 0.75 6.68 49.03 2979 32292 0.17 125.17 17137.63
- tasklist_lock-W: 15 15 1.45 10.87 32.70 1201 7390 0.58 62.55 13648.47
+ clockevents_lock: 2926159 2947636 0.15 46882.81 1784540466.34 605.41 3381345 3879161 0.00 2260.97 53178395.68 13.71
+ tick_broadcast_lock: 346460 346717 0.18 2257.43 39364622.71 113.54 3642919 4242696 0.00 2263.79 49173646.60 11.59
+ &mapping->i_mmap_mutex: 203896 203899 3.36 645530.05 31767507988.39 155800.21 3361776 8893984 0.17 2254.15 14110121.02 1.59
+ &rq->lock: 135014 136909 0.18 606.09 842160.68 6.15 1540728 10436146 0.00 728.72 17606683.41 1.69
+ &(&zone->lru_lock)->rlock: 93000 94934 0.16 59.18 188253.78 1.98 1199912 3809894 0.15 391.40 3559518.81 0.93
+ tasklist_lock-W: 40667 41130 0.23 1189.42 428980.51 10.43 270278 510106 0.16 653.51 3939674.91 7.72
+ tasklist_lock-R: 21298 21305 0.20 1310.05 215511.12 10.12 186204 241258 0.14 1162.33 1179779.23 4.89
+ rcu_node_1: 47656 49022 0.16 635.41 193616.41 3.95 844888 1865423 0.00 764.26 1656226.96 0.89
+ &(&dentry->d_lockref.lock)->rlock: 39791 40179 0.15 1302.08 88851.96 2.21 2790851 12527025 0.10 1910.75 3379714.27 0.27
+ rcu_node_0: 29203 30064 0.16 786.55 1555573.00 51.74 88963 244254 0.00 398.87 428872.51 1.76

Clear the statistics:

diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index b2c71c5..ab296f2 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -421,6 +421,7 @@ static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
seq_time(m, lt->min);
seq_time(m, lt->max);
seq_time(m, lt->total);
+ seq_time(m, lt->nr ? lt->total/lt->nr : 0);
}

static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
@@ -518,20 +519,20 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
}
if (i) {
seq_puts(m, "\n");
- seq_line(m, '.', 0, 40 + 1 + 10 * (14 + 1));
+ seq_line(m, '.', 0, 40 + 1 + 12 * (14 + 1));
seq_puts(m, "\n");
}
}

static void seq_header(struct seq_file *m)
{
- seq_printf(m, "lock_stat version 0.3\n");
+ seq_printf(m, "lock_stat version 0.4\n");

if (unlikely(!debug_locks))
seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n");

- seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
- seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s "
+ seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
+ seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s %14s %14s "
"%14s %14s\n",
"class name",
"con-bounces",
@@ -539,12 +540,14 @@ static void seq_header(struct seq_file *m)
"waittime-min",
"waittime-max",
"waittime-total",
+ "waittime-avg",
"acq-bounces",
"acquisitions",
"holdtime-min",
"holdtime-max",
- "holdtime-total");
- seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
+ "holdtime-total",
+ "holdtime-avg");
+ seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
seq_printf(m, "\n");
}

--
1.8.1.4




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