lockstat 提供了全局的lock统计信息，可以对全系统的所有锁类竞争情况，持锁情况进行统计。
- /kernel/locking/lockdep.c // CONFIG_LOCK_STAT
1、使能
Enable CONFIG_LOCK_STAT
2、开启/关闭
echo 1 >/proc/sys/kernel/lock_stat
echo 0 >/proc/sys/kernel/lock_stat
3、查看
less /proc/lock_stat
4、阅读
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: 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
10 &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
con-bounces - The number of contended lock acquisitions which involved cross-cpu data.
contentions - 等锁次数
waittime-min - 最低等待时间(us)
waittime-max - 最大等待时间(us)
waittime-total - 总等待时间(us)
acq-bounces - The number of lock acquisitions which involved cross-cpu data.
acquisitions - 持锁次数
holdtime-min - 最低持锁时间(us)
holdtime-max - 最大持锁时间(us)
holdtime-total - 总持锁时间(us)
表中包含两组锁类，每组为一个锁类的统计，每组分为三部分，第一部分为锁类的整体统计，第二部为四处Try to get the lock的位置，第三部分为四处Lock holder的位置，这几处位置并不是全部数据，可能丢失其他位置。
5、竞争最激烈的十个锁类
grep : /proc/lock_stat | head
https://docs.kernel.org/locking/lockstat.html
https://groups.google.com/g/linuxkernelnewbies/c/6BJYVrHHh8U