From owner-freebsd-arch@FreeBSD.ORG Sat Mar 20 15:20:16 2010 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 317931065670; Sat, 20 Mar 2010 15:20:16 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from mail-fx0-f224.google.com (mail-fx0-f224.google.com [209.85.220.224]) by mx1.freebsd.org (Postfix) with ESMTP id 8E86E8FC1C; Sat, 20 Mar 2010 15:20:15 +0000 (UTC) Received: by fxm24 with SMTP id 24so257789fxm.3 for ; Sat, 20 Mar 2010 08:20:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:subject:x-enigmail-version:content-type :content-transfer-encoding; bh=vvUN2xXU6OfXsVRUp5YJ/fHgtbXc4qLggljTqGUJHzM=; b=l2xWHqKVDMhy0h3pjpoYeVZYgw2weLpUcDINbSeH/syIdaZx2WxbWLRc1NBGeEXIBx LWYKuoJIGHbDha/poyUDwtgEFxzSI80tzBH/JorKCo2WzmZ2ZVWLBLtBneAhOLrHcL6j Q9/3xUi9fo44vT1Elrp1kp+f8WjMek7JanWrY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:subject :x-enigmail-version:content-type:content-transfer-encoding; b=lAPsAIn/5L3pYShmDw3PvEBdqm+Z8tjl8/0PklhBllDE5Y+boYGlNxe+HgFlVPgFzY 4NZWE+uejFZSI1mhGQZoLLUV067fyxmd3UD0rQ6pu6+chi+c46q1ppBU/6w6kJLT6M3g DYontRp3el1393VFELR+HRbBacEIaEEijtO3I= Received: by 10.223.132.197 with SMTP id c5mr890792fat.35.1269098412629; Sat, 20 Mar 2010 08:20:12 -0700 (PDT) Received: from mavbook.mavhome.dp.ua (pc.mavhome.dp.ua [212.86.226.226]) by mx.google.com with ESMTPS id 16sm182270fxm.12.2010.03.20.08.20.11 (version=SSLv3 cipher=RC4-MD5); Sat, 20 Mar 2010 08:20:12 -0700 (PDT) Sender: Alexander Motin Message-ID: <4BA4E7A9.3070502@FreeBSD.org> Date: Sat, 20 Mar 2010 17:20:09 +0200 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: FreeBSD-Current , freebsd-arch@freebsd.org X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Cc: Subject: Increasing MAXPHYS X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 20 Mar 2010 15:20:16 -0000 Hi. With set of changes done to ATA, CAM and GEOM subsystems last time we may now get use for increased MAXPHYS (maximum physical I/O size) kernel constant from 128K to some bigger value. Increasing it allows to improve performance and reduce processing overhead for large I/O operations. Potential downside is a bit increased kernel memory usage, but as soon as these values were not changing for more than 8 years, I don't think it should be significant now. Present state of things: - ahci(4) and siis(4) support any I/O sizes up to MAXPHYS; - ata(4) supports I/O sizes up to min(512K, MAXPHYS) for the most of controllers, and works correctly for the rest; - most of SCSI controller drivers still limited by DFLTPHYS, but parts needed to work on them one by one later are already in place. - ad(4), da(4), ada(4), cd(4), acd(4), afd(4), atapicam(4) drivers support any I/O sizes, supported by underlying hardware and reported by ata(4) and cam(4) subsystems; - gmirror(4), gstripe(4), graid3(4), gconcat(4) were tested and fixed to support any I/O sizes up to MAXPHYS; All above I have successfully tested last months with MAXPHYS of 1MB on i386 and amd64 platforms. So my questions are: - does somebody know any issues denying increasing MAXPHYS in HEAD? - are there any specific opinions about value? 512K, 1MB, MD? -- Alexander Motin