From owner-svn-src-all@FreeBSD.ORG Tue Mar 3 17:27:47 2015 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 57AAD1FF; Tue, 3 Mar 2015 17:27:47 +0000 (UTC) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "gold.funkthat.com", Issuer "gold.funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 2DFB2BF7; Tue, 3 Mar 2015 17:27:46 +0000 (UTC) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.14.5/8.14.5) with ESMTP id t23HRk86063043 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 3 Mar 2015 09:27:46 -0800 (PST) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.14.5/8.14.5/Submit) id t23HRjmJ063042; Tue, 3 Mar 2015 09:27:45 -0800 (PST) (envelope-from jmg) Date: Tue, 3 Mar 2015 09:27:45 -0800 From: John-Mark Gurney To: Julian Elischer Subject: Re: svn commit: r279539 - head/sys/sys Message-ID: <20150303172745.GO32329@funkthat.com> References: <201503022005.t22K5HTL062907@svn.freebsd.org> <54F57CC6.9050109@freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54F57CC6.9050109@freebsd.org> X-Operating-System: FreeBSD 9.1-PRERELEASE amd64 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (gold.funkthat.com [127.0.0.1]); Tue, 03 Mar 2015 09:27:46 -0800 (PST) Cc: Davide Italiano , "svn-src-head@freebsd.org" , "svn-src-all@freebsd.org" , "src-committers@freebsd.org" , Neel Natu X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Mar 2015 17:27:47 -0000 Julian Elischer wrote this message on Tue, Mar 03, 2015 at 01:20 -0800: > On 3/2/15 4:55 PM, Neel Natu wrote: > > Hi Davide, > > > > On Mon, Mar 2, 2015 at 12:26 PM, Davide Italiano wrote: > >> On Mon, Mar 2, 2015 at 12:05 PM, John-Mark Gurney wrote: > >>> Author: jmg > >>> Date: Mon Mar 2 20:05:16 2015 > >>> New Revision: 279539 > >>> URL: https://svnweb.freebsd.org/changeset/base/279539 > >>> > >>> Log: > >>> give others fair warning that _SPARE2 isn't just cxgb, but used by large > >>> number of other subsystems, so you probably don't want _SPARE2.. > >>> > >>> ktr needs an overhaul to really only compile in the ones you want, > >>> we've long passed the 31 bits it provides.. > >>> > >> If you really want to do the overhaul (which would be honestly great), > >> I might consider revamping my work for per-cpu KTR buffer and include > >> that in the change. Originally it was just an exercise, but then it > >> evolved and I've been sitting with it in my local tree for a while. I > >> never had the chutzpah to upstream it because it involves fundamental > >> changes and breaks compatibility with the old ktrdump(1) format. > >> A rather outdated (and maybe not completely functional) version of the > >> patch can be found here: > >> http://people.freebsd.org/~davide/locking/ktr_percpu.4.diff , which > >> should give you an high level view of the change. > >> I can update it to the last version and bring up for review, if > >> somebody think it might be a sane idea avoiding synchronization on a > >> single buffer for KTR. > I think it would be a problem... > one of the truely useful things about ktr is that it does use a single > buffer. > this means that you get the true interaction between CPUS. > Schedgraph relies on this (as one example). Don't some systems provide a syncronized P-state invariant TSC? If so, we can use the TSC clock to tell ordering between cores.. I could definately seeing it be a tunable that lets people force either single buffer, or PCPU buffer KTR... Where we know TSC is syncronized, we default to PCPU and others a single buffer... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."