From owner-freebsd-performance@FreeBSD.ORG Sun Feb 19 04:35:27 2006 Return-Path: X-Original-To: freebsd-performance@freebsd.org Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8F56216A422 for ; Sun, 19 Feb 2006 04:35:27 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from mh2.centtech.com (moat3.centtech.com [207.200.51.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id E9A3343D60 for ; Sun, 19 Feb 2006 04:35:24 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from [192.168.42.21] (andersonbox1.centtech.com [192.168.42.21]) by mh2.centtech.com (8.13.1/8.13.1) with ESMTP id k1J4ZN95065054 for ; Sat, 18 Feb 2006 22:35:23 -0600 (CST) (envelope-from anderson@centtech.com) Message-ID: <43F7F58C.3020908@centtech.com> Date: Sat, 18 Feb 2006 22:35:24 -0600 From: Eric Anderson User-Agent: Thunderbird 1.5 (X11/20060112) MIME-Version: 1.0 To: freebsd-performance@freebsd.org References: <20060219040656.GT2756@rabbit> <20060219041752.GU2756@rabbit> In-Reply-To: <20060219041752.GU2756@rabbit> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV 0.87.1/1292/Fri Feb 17 03:39:02 2006 on mh2.centtech.com X-Virus-Status: Clean Subject: Re: stat speed X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 19 Feb 2006 04:35:27 -0000 Mark Bucciarelli wrote: > On Sat, Feb 18, 2006 at 11:06:57PM -0500, Mark Bucciarelli wrote: > >> I'm curious how fast stat is. >> >> I generated a list of 200,000 file names >> >> # find / | head -200000 > files.statspeed >> >> then ran a million iterations of randomly picking a file name and >> stating it (see attached program). >> > > Hmmm, 200,000 files 1,000,000 iterations. On avg, each file hit > five times. Uhh, that's not a good way to avoid caching. Doh. > > Wow, caching is pretty amazing. I just reran the program, this time > using 500,000 file paths and only stat'ing 10,000 of them. > > The first run was 99,059/second, the second was 188,239. > > So I guess 100,000/second is about right on my system w/o cache. > I'm also wondering if by using find, and getting a list of files/directories in the default order, you might be seeing some results that aren't really completely random. What I mean is, your find is traversing the tree, probably digging through directories based on inode number or last modified time (can't recall which), but either way, it's possible your list consisted of clumps of files/dirs in the same cylinder groups, specially since you grabbed the first 500k files, instead of picking a random file from the entire list of files on the filesystem, and building a list from that random plucking.. This is all speculative, but if you had lots of files in a directory, those could be clumped in a few cylinder groups and therefore you might see higher numbers than sampling from the entire disk (since the speed is probably mostly dominated by disk seeks I believe). What exactly are you trying to determine? Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------