Date: Fri, 28 Mar 2014 20:30:55 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Ed Maste <emaste@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r263878 - head/sys/amd64/amd64 Message-ID: <20140328183055.GA21331@kib.kiev.ua> In-Reply-To: <CAPyFy2A=mYfpFkkXy4xSOE-qfnLT6v4K0zh2SpuiWX99DPb=QQ@mail.gmail.com> References: <201403281607.s2SG7Ri9052922@svn.freebsd.org> <CAPyFy2A=mYfpFkkXy4xSOE-qfnLT6v4K0zh2SpuiWX99DPb=QQ@mail.gmail.com>
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--l+LxDeyHMCBjwres Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 28, 2014 at 01:23:06PM -0400, Ed Maste wrote: > On 28 March 2014 12:07, Konstantin Belousov <kib@freebsd.org> wrote: > > Author: kib > > Date: Fri Mar 28 16:07:27 2014 > > New Revision: 263878 > > URL: http://svnweb.freebsd.org/changeset/base/263878 > > > > Log: > > Several fixes for the PCID implementation: >=20 > I'd like to revert r262765 (where I disabled it by default) to get > broader testing on this; do you see any reason I should wait instead? I am on edge there. =46rom one side, enabling PCID degrades the pgbench (?) by 10% at least on many-cores machines. This is understandable, since committed implementation keeps track of the cpus which has translation information cached for the given pmap, and invalidation IPIs must be broadcasted to the whole set of the cpus. The set is larger than the set of cpus for which the pmap is active, so the overhead from TLB shootdown is larger. On the other side, on the desktop-class hw, i.e. 4 cores/8 threads, there is no significant degradation, AFAIR. And, in microbenchmarks, the context switch latency is improved up to 2 times regardless of the machine class. So I initially delayed disabling the PCID, after the pgbench results were published, but now I similarly do now want much to change the defaults back to enabled. Might be, do it in HEAD only ? --l+LxDeyHMCBjwres Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iQIcBAEBAgAGBQJTNb/eAAoJEJDCuSvBvK1BykwP/RJMCcelv1LTYL4OloehWPl6 4ZFrSYEo+sLGNw6NfOYY5e4/uTyb52WmB3nJVuFEiw7PPeCcL8EpTn7Gb6tmRmtU ya1shp0zbxc2dhuLLvw/U4eXt3Qr3rG4k1LuUsEAT8rRw+B55gRvpy8lTJJSRPEk QLKrUEHPM8ND8hl1rw4h+c8jlGQ4Q4VCeVgZUVaKwOdEM1gDom8JBqUMtpdVEi1R VEdHflg1u4ghIzgqmCTHIa+I1e9VrJzJtm1x9DatBtgp2xyq4lzhxRjtxh+kDKUv ouqLJ4L8LG48ADtpfvK2+/OgVqnrm7yDu2986/2hZv2WGc3uSMkbmR2ECAeS+zUC T7rPdAsx0z8EKH7Vap/veGo2juwN/3SzNmru/hWHFVwtnFxeQQ5rYlClzAtwiGEd 17e4toYRiZa8Dq+kkNKlFu+pblkC0jZVWPqdgovLpI7TECWYZR6r/Znu2qF1rEj7 /ANjdnZRkbwu1UUEgUDYVJGMpijUaAqonqU7LfUFG7L9teRe0w695LRtfmn5gAIQ N3m+ZDd9Dn5Ce29WXBmumu6gaknB6mS5VqG1IARyUpCyDF6htX9Jzid/GR+zkW32 Mk3wLWSpbG0x5MYjEu+xwkpZTx9UPNOScMSGcBspGDH6JhEh/7YSv5lNG0Wf0PA0 TtMN7llsnNg2m19FMkGA =CeEG -----END PGP SIGNATURE----- --l+LxDeyHMCBjwres--
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