From owner-freebsd-current@FreeBSD.ORG Sun Jan 8 22:21:52 2012 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D0BB51065701 for ; Sun, 8 Jan 2012 22:21:52 +0000 (UTC) (envelope-from phk@phk.freebsd.dk) Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222]) by mx1.freebsd.org (Postfix) with ESMTP id 8F3508FC1B for ; Sun, 8 Jan 2012 22:21:52 +0000 (UTC) Received: from critter.freebsd.dk (critter.freebsd.dk [192.168.61.3]) by phk.freebsd.dk (Postfix) with ESMTP id 47D605DD5 for ; Sun, 8 Jan 2012 22:21:51 +0000 (UTC) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.14.5/8.14.5) with ESMTP id q08MLoNA008335 for ; Sun, 8 Jan 2012 22:21:51 GMT (envelope-from phk@phk.freebsd.dk) To: current@freebsd.org From: Poul-Henning Kamp Content-Type: text/plain; charset=ISO-8859-1 Date: Sun, 08 Jan 2012 22:21:50 +0000 Message-ID: <8334.1326061310@critter.freebsd.dk> Cc: Subject: CD9660/md(4)/UFS22 silly behaviour X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 08 Jan 2012 22:21:52 -0000 I'm doing som data-mining on a pile of ISO images right now. I stuck the ISOs on a UFS2 on a flash-disk for speed, and mdconfig(8)'d them so I could mount them. The traffic pattern his "interesting": dT: 1.003s w: 1.000s L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name [...] 1 733 733 1466 1.3 0 0 0.0 98.2| md39 1 733 733 23449 1.3 0 0 0.0 93.2| da0 Notice the 1:16 ratio on kBps but 1:1 ratio on ops/s ? da0's UFS2 has 32k block-size: magic 19540119 (UFS2) time Wed Jan 4 16:41:47 2012 superblock location 65536 id [ 4f046cf5 c30697ee ] ncg 104 size 19537685 blocks 19228156 bsize 32768 shift 15 mask 0xffff8000 fsize 4096 shift 12 mask 0xfffff000 [...] It looks like every 2k read from CD9660 turns into a 32k block read in the UFS filesystem, without any beneficial caching happening. Less than optimal I'd say... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.