Date: Sat, 27 Aug 2016 00:36:13 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Adrian Chadd <adrian@freebsd.org> 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: <20160826213613.GH88122@zxy.spb.ru> In-Reply-To: <CAJ-Vmomg6ejJdZessaUU3DF%2BV%2BsQd=hMZwo_pDYpa4XjoB_ZcA@mail.gmail.com> 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>
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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? > > 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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