Date: Fri, 26 Aug 2016 14:42:27 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: Bruce Simpson <bms@fastmail.net>, Ryan Stone <rysto32@gmail.com>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, Ryan Stone <rstone@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org> Subject: Re: svn commit: r304436 - in head: . sys/netinet Message-ID: <CAJ-VmomRDdg5EUUiAHOyVBzitd8cZ8bPGCrU9btnveWeW-_85g@mail.gmail.com> In-Reply-To: <20160826213613.GH88122@zxy.spb.ru> References: <0f42c5fb-f930-c6e3-75d6-df97f67c201d@fastmail.net> <20160820204106.GW8192@zxy.spb.ru> <0acba141-4701-d9c2-0ddb-46d1f60ff55b@fastmail.net> <20160820220510.GX8192@zxy.spb.ru> <8ac23bd1-dcb3-7c64-f195-5039f9af0eaf@fastmail.net> <20160821000400.GY8192@zxy.spb.ru> <20160826144926.GE88122@zxy.spb.ru> <3dba1b70-54cc-0bb1-5cc8-8c56cd750bec@fastmail.net> <20160826151324.GF88122@zxy.spb.ru> <CAJ-Vmomg6ejJdZessaUU3DF%2BV%2BsQd=hMZwo_pDYpa4XjoB_ZcA@mail.gmail.com> <20160826213613.GH88122@zxy.spb.ru>
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On 26 August 2016 at 14:36, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote: > On Fri, Aug 26, 2016 at 02:32:00PM -0700, Adrian Chadd wrote: > >> Hi, >> >> It's pcb lock contention. > > Not sure: only 5% of all time. > And same 5% for tcbhashsize = 65K and 256K. > Or you talk about some more thin effect? You're in the inpcb lock from multiple places. the tcbhashsize doesnt influence the pcb lock contention - it just affects how long you take doing lookups. iF your hash table is too small then you end up doing lots of O(n) walks of a hash bucket to find a pcb entry. :) -adrian >> >> On 26 August 2016 at 08:13, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote: >> > On Fri, Aug 26, 2016 at 04:01:14PM +0100, Bruce Simpson wrote: >> > >> >> Slawa, >> >> >> >> I'm afraid this may be a bit of a non-sequitur. Sorry.. I seem to be >> >> missing something. As I understand it this thread is about Ryan's change >> >> to netinet for broadcast. >> >> >> >> On 26/08/16 15:49, Slawa Olhovchenkov wrote: >> >> > On Sun, Aug 21, 2016 at 03:04:00AM +0300, Slawa Olhovchenkov wrote: >> >> >> On Sun, Aug 21, 2016 at 12:25:46AM +0100, Bruce Simpson wrote: >> >> >>> Whilst I agree with your concerns about multipoint, I support the >> >> >>> motivation behind Ryan's original change: optimize the common case. >> >> >> >> >> >> Oh, common case... >> >> >> I am have pmc profiling for TCP output and see on this SVG picture and >> >> >> don't find any simple way. >> >> >> You want to watch too? >> >> > >> >> > At time peak network traffic (more then 25K connections, about 20Gbit >> >> > total traffic) half of cores fully utilised by network stack. >> >> > >> >> > This is flamegraph from one core: http://zxy.spb.ru/cpu10.svg >> >> > This is same, but stack cut of at ixgbe_rxeof for more unified >> >> > tcp/ip stack view http://zxy.spb.ru/cpu10u.svg >> >> ... >> >> >> >> I appreciate that you've taken the time to post a flamegraph (a >> >> fashionable visualization) of relative performance in the FreeBSD >> >> networking stack. >> >> >> >> Sadly, I am mostly out of my depth for looking at stack wide performance >> >> for the moment; for the things I look at involving FreeBSD at work just >> >> at the moment, I would not generally go down there except for specific >> >> performance issues (e.g. with IEEE 1588). >> >> >> >> It sounds as though perhaps you should raise a wider discussion about >> >> your results on -net. I would caution you however that the Function >> >> Boundary Trace (FBT) provider for DTrace can introduce a fair amount of >> >> noise to the raw performance data because of the trap mechanism it uses. >> >> This ruled it out for one of my own studies requiring packet-level accuracy. >> >> >> >> Whilst raw pmc(4) profiles may require more post-processing, they will >> >> provide less equivocal data (and a better fix) on the hot path, due also >> >> to being sampled effectively on a PMC interrupt (a gather stage- poll >> >> core+uncore MSRs), not purely a software timer interrupt. >> > >> > Thanks for answer, I am now try to start discussion on -net.
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