Date: Fri, 26 Aug 2016 14:32:00 -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-Vmomg6ejJdZessaUU3DF%2BV%2BsQd=hMZwo_pDYpa4XjoB_ZcA@mail.gmail.com> In-Reply-To: <20160826151324.GF88122@zxy.spb.ru> References: <CAFMmRNy-e1uzdtz2cb5DAa9kRd%2BkHg%2BmWbf=HNDWVdGGjOPUWA@mail.gmail.com> <eb4c228e-8efe-b519-e85b-87800b3ec7a1@fastmail.net> <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>
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Hi, It's pcb lock contention. -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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