From owner-svn-src-all@FreeBSD.ORG Sun Jan 4 19:06:43 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 C37D4841; Sun, 4 Jan 2015 19:06:43 +0000 (UTC) Received: from mail-wi0-x233.google.com (mail-wi0-x233.google.com [IPv6:2a00:1450:400c:c05::233]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 533EBD1E; Sun, 4 Jan 2015 19:06:43 +0000 (UTC) Received: by mail-wi0-f179.google.com with SMTP id ex7so2049421wid.12; Sun, 04 Jan 2015 11:06:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=YZCQj/4NPzrOXN3Fty4xeSmzn6w8NzUz1Q03uxxUOyk=; b=xEZyjS5+cqIkC+NC+NA26LZP6ZSnZCeE4KREx6FJBHh9mDHC+j+T48OBHHpVVXA22b 2FFki1rmKq0qOZjyQOOeVc3eyRK8QVD/RXpdP4iR52/C+XuO4vknD1YCcbjmMrcKF8iN am9meKdpk95R1KUHx9Nw6NtirelfGbWwNaF/t32+DUgq4Vp3enyUYnswP/8io5WDFsCr WrCZsbneSDZ78Vu2QjPxQjRDGnBR7D/xr2KT87twVOLExjWNpGNVT2GmWK+Qv1XfcSPF Adolucqx9MjH7GlhenMPm2VlwJrIjv+m4NAic426xFHtL3hC6MyoP4xllEG3Xvp6y9UV cWww== X-Received: by 10.180.75.42 with SMTP id z10mr18374627wiv.70.1420398401608; Sun, 04 Jan 2015 11:06:41 -0800 (PST) Received: from dft-labs.eu (n1x0n-1-pt.tunnel.tserv5.lon1.ipv6.he.net. [2001:470:1f08:1f7::2]) by mx.google.com with ESMTPSA id q10sm62715028wjx.34.2015.01.04.11.06.39 (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Sun, 04 Jan 2015 11:06:40 -0800 (PST) Date: Sun, 4 Jan 2015 20:06:37 +0100 From: Mateusz Guzik To: "Bjoern A. Zeeb" Subject: Re: svn commit: r276424 - head/sys/kern Message-ID: <20150104190637.GA5807@dft-labs.eu> References: <201412302140.sBULek5f076019@svn.freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org 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: Sun, 04 Jan 2015 19:06:43 -0000 On Tue, Dec 30, 2014 at 10:45:43PM +0000, Bjoern A. Zeeb wrote: > > > On 30 Dec 2014, at 21:40 , Mateusz Guzik wrote: > > > > Author: mjg > > Date: Tue Dec 30 21:40:45 2014 > > New Revision: 276424 > > URL: https://svnweb.freebsd.org/changeset/base/276424 > > > > Log: > > Convert vfs hash lock from a mutex to an rwlock. > > This is very obvious from the change. > > What is not and should be described as well is some of this: > > - Why? > - What are the benefits? > - What are the locking implications? > - Does it make a performance difference? If yes, was it measured? > - … (you got the idea) > Sorry for late reply. This is just one of many minor things which showed up in lock profiling during make -j 40 buildkernel. I don't expect the gain to be quite noticeable (at least not now since there way more serious bottlenecks), thus there are no claims stuff is way faster in the commit message. This change is entirely transparent to callers and callees. -- Mateusz Guzik