Date: Mon, 26 Sep 2016 13:57:03 +0200 From: Julien Charbon <jch@freebsd.org> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: Konstantin Belousov <kostikbel@gmail.com>, freebsd-stable@FreeBSD.org, hiren panchasara <hiren@strugglingcoder.info> Subject: Re: 11.0 stuck on high network load Message-ID: <064be3ae-8df9-fa22-06ab-346af024afd3@freebsd.org> In-Reply-To: <20160925124626.GI2840@zxy.spb.ru> References: <20160916183053.GL9397@strugglingcoder.info> <20160916190330.GG2840@zxy.spb.ru> <78cbcdc9-f565-1046-c157-2ddd8fcccc62@freebsd.org> <20160919204328.GN2840@zxy.spb.ru> <8ba75d6e-4f01-895e-0aed-53c6c6692cb9@freebsd.org> <20160920202633.GQ2840@zxy.spb.ru> <f644cd52-4377-aa90-123a-3a2887972bbc@freebsd.org> <20160921195155.GW2840@zxy.spb.ru> <e4e0188c-b22b-29af-ed15-b650c3ec4553@gmail.com> <20160923200143.GG2840@zxy.spb.ru> <20160925124626.GI2840@zxy.spb.ru>
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Hi Slawa, On 9/25/16 2:46 PM, Slawa Olhovchenkov wrote: > On Fri, Sep 23, 2016 at 11:01:43PM +0300, Slawa Olhovchenkov wrote: >> On Wed, Sep 21, 2016 at 11:25:18PM +0200, Julien Charbon wrote: >>> >>> On 9/21/16 9:51 PM, Slawa Olhovchenkov wrote: >>>> 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 >>>> ------------------------------------------------------------------------------- >>> >>> This is interesting, it seems that you have two call paths competing >>> for INP locks here: >>> >>> - pfslowtimo()/tcp_tw_2msl_scan(reuse=0) and >>> >>> - tcp_input()/tcp_twstart()/tcp_tw_2msl_scan(reuse=1) >> >> My current hypothesis: >> >> nginx do write() (or may be close()?) to socket, kernel lock >> first inp in V_twq_2msl, happen callout for pfslowtimo() on the same >> CPU core and tcp_tw_2msl_scan infinity locked on same inp. >> >> In this case you modification can't help, before next try we need some >> like yeld(). > > Or may be locks leaks. > Or both. Actually one extra debug thing you can do is launching lockstat with below extra options: -H For Hold lock stats -P To get the overall time -s 20 To get the stackstrace To see who is holding the INP lock for so long. Thanks to Hiren for pointing the -H option. -- Julien
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