On Wed, Sep 21, 2016 at 09:11:24AM +0200, Julien Charbon wrote:
>
> You can also use Dtrace and lockstat (especially with the lockstat -s
> option):
>
> https://wiki.freebsd.org/DTrace/One-Liners#Kernel_Locks
> https://www.freebsd.org/cgi/man.cgi?query=lockstat&manpath=FreeBSD+11.0-RELEASE
>
> But I am less familiar with Dtrace/lockstat tools.
I am still use old kernel and got lockdown again.
Try using lockstat (I am save more output), interesting may be next:
R/W writer spin on writer: 190019 events in 1.070 seconds (177571 events/sec)
-------------------------------------------------------------------------------
Count indv cuml rcnt nsec Lock Caller
140839 74% 74% 0.00 24659 tcpinp tcp_tw_2msl_scan+0xc6
nsec ------ Time Distribution ------ count Stack
4096 | 913 tcp_twstart+0xa3
8192 |@@@@@@@@@@@@ 58191 tcp_do_segment+0x201f
16384 |@@@@@@ 29594 tcp_input+0xe1c
32768 |@@@@ 23447 ip_input+0x15f
65536 |@@@ 16197
131072 |@ 8674
262144 | 3358
524288 | 456
1048576 | 9
-------------------------------------------------------------------------------
Count indv cuml rcnt nsec Lock Caller
49180 26% 100% 0.00 15929 tcpinp tcp_tw_2msl_scan+0xc6
nsec ------ Time Distribution ------ count Stack
4096 | 157 pfslowtimo+0x54
8192 |@@@@@@@@@@@@@@@ 24796 softclock_call_cc+0x179
16384 |@@@@@@ 11223 softclock+0x44
32768 |@@@@ 7426
intr_event_execute_handlers+0x95
65536 |@@ 3918
131072 | 1363
262144 | 278
524288 | 19
-------------------------------------------------------------------------------
> >> #1. Try above kernel options at least once, and see what you can get.
> >
> > OK, I am try this after some time.
> >
> >> #2. If #1 is a total failure try below patch: It won't solve anything,
> >> it just makes tcp_tw_2msl_scan() less greedy when there is contention on
> >> the INP write lock. If it makes the debugging more feasible, continue
> >> to #3.
> >
> > OK, thanks.
> > What purpose to not skip locked tcptw in this loop?
>
> If I understand your question correctly: According to your pmcstat
> result, tcp_tw_2msl_scan() currently struggles with a write lock
> (__rw_wlock_hard) and the only write lock used tcp_tw_2msl_scan() is
> INP_WLOCK. No sign of contention on TW_RLOCK(V_tw_lock) currently.
>
> 51.86% [2413083] lock_delay @ /boot/kernel.VSTREAM/kernel
> 100.0% [2413083] __rw_wlock_hard
> 100.0% [2413083] tcp_tw_2msl_scan
>
> --
> Julien
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