Date: Wed, 27 May 2015 14:06:20 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Kurt Lidl <lidl@pix.net> Cc: Bruce Evans <brde@optusnet.com.au>, Eitan Adler <eadler@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r281103 - head/sys/amd64/amd64 Message-ID: <20150527210619.GA50817@funkthat.com> In-Reply-To: <5565CC49.1020800@pix.net> References: <201504050518.t355IFVJ001786@svn.freebsd.org> <20150405163305.A2515@besplex.bde.org> <CAF6rxgkZA=GbyQFhQC63c9z%2By_ki%2Byjt6fZW%2BP9cHve5L=pYoA@mail.gmail.com> <20150406152653.K1066@besplex.bde.org> <5565CC49.1020800@pix.net>
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Kurt Lidl wrote this message on Wed, May 27, 2015 at 09:53 -0400: > On 4/6/15 1:42 AM, Bruce Evans wrote: > > On Mon, 6 Apr 2015, Eitan Adler wrote: > > > >> + a few people interested in the diff > >> > >> On 5 April 2015 at 02:55, Bruce Evans <brde@optusnet.com.au> wrote: > >>> On Sun, 5 Apr 2015, Eitan Adler wrote: > >> > >> I did not confirm the performance impact, but the submitter and others > >> indicated they saw a difference. > >> > >> Do you have specific data that shows that there was an improvement? > > > > Only micro-benchmark output that indicates little difference. This > > is probably very MD (depending on write combining hardware), so you > > might only see a difference on some systems. > > > > I also have micro-benchmark output for network packets/second that > > shows 10% differences for the change of adding 1 byte of padding > > in code that is never executed. This seems to be due to different > > cache misses. To eliminate differences from this (except ones > > caused by actually running different code), create a reference > > version by padding the functions or data to be changed so that > > the change doesn't affect the address of anything except the > > internals of the changed parts. > > > > I might try a makeworld run to see if changing the non-temporal > > accesses in pagecopy and pagezero to cached. > > > I ran a few (total of 12) buildworld runs after this discussion. > I finally got around to posting the results to the original bug. > > The data is here: > > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199151#c3 If you run ministat on the real results, there won't be a difference w/ 95% confidence... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."
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