diff options
Diffstat (limited to 'Documentation/lockstat.txt')
| -rw-r--r-- | Documentation/lockstat.txt | 140 |
1 files changed, 99 insertions, 41 deletions
diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt index 4ba4664ce5c..72d01068975 100644 --- a/Documentation/lockstat.txt +++ b/Documentation/lockstat.txt @@ -12,8 +12,9 @@ Because things like lock contention can severely impact performance. - HOW Lockdep already has hooks in the lock functions and maps lock instances to -lock classes. We build on that. The graph below shows the relation between -the lock functions and the various hooks therein. +lock classes. We build on that (see Documentation/lockdep-design.txt). +The graph below shows the relation between the lock functions and the various +hooks therein. __acquire | @@ -45,16 +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). @@ -62,8 +61,20 @@ applicable). It also tracks 4 contention points per class. A contention point is a call site that had to wait on lock acquisition. + - CONFIGURATION + +Lock statistics are enabled via CONFIG_LOCK_STAT. + - USAGE +Enable collection of statistics: + +# echo 1 >/proc/sys/kernel/lock_stat + +Disable collection of statistics: + +# echo 0 >/proc/sys/kernel/lock_stat + Look at the current lock statistics: ( line numbers not part of actual output, done for clarity in the explanation @@ -71,49 +82,96 @@ Look at the current lock statistics: # less /proc/lock_stat -01 lock_stat version 0.2 -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 &inode->i_data.tree_lock-W: 15 21657 0.18 1093295.30 11547131054.85 58 10415 0.16 87.51 6387.60 -07 &inode->i_data.tree_lock-R: 0 0 0.00 0.00 0.00 23302 231198 0.25 8.45 98023.38 -08 -------------------------- -09 &inode->i_data.tree_lock 0 [<ffffffff8027c08f>] add_to_page_cache+0x5f/0x190 -10 -11 ............................................................................................................................................................................................... -12 -13 dcache_lock: 1037 1161 0.38 45.32 774.51 6611 243371 0.15 306.48 77387.24 -14 ----------- -15 dcache_lock 180 [<ffffffff802c0d7e>] sys_getcwd+0x11e/0x230 -16 dcache_lock 165 [<ffffffff802c002a>] d_alloc+0x15a/0x210 -17 dcache_lock 33 [<ffffffff8035818d>] _atomic_dec_and_lock+0x4d/0x70 -18 dcache_lock 1 [<ffffffff802beef8>] shrink_dcache_parent+0x18/0x130 +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............................................................................................................................................................................................................................. +20 +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 -show the header with column descriptions. Lines 05-10 and 13-18 show the actual +show the header with column descriptions. Lines 05-18 and 20-31 show the actual statistics. These statistics come in two parts; the actual stats separated by a -short separator (line 08, 14) from the contention points. +short separator (line 08, 13) from the contention points. -The first lock (05-10) is a read/write lock, and shows two lines above the +The first lock (05-18) is a read/write lock, and shows two lines above the short separator. The contention points don't match the column descriptors, -they have two: contentions and [<IP>] symbol. - +they have two: contentions and [<IP>] symbol. The second set of contention +points are the points we're contending with. + +The integer part of the time values is in us. + +Dealing with nested locks, subclasses may appear: + +32........................................................................................................................................................................................................................... +33 +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 +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 +45 +46........................................................................................................................................................................................................................... +47 +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 +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 + +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, +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_lock: 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: |