From owner-freebsd-hackers@FreeBSD.ORG Wed Jul 14 07:04:59 2010 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5ADF21065672 for ; Wed, 14 Jul 2010 07:04:59 +0000 (UTC) (envelope-from gljennjohn@googlemail.com) Received: from mail-bw0-f54.google.com (mail-bw0-f54.google.com [209.85.214.54]) by mx1.freebsd.org (Postfix) with ESMTP id D64248FC08 for ; Wed, 14 Jul 2010 07:04:58 +0000 (UTC) Received: by bwz12 with SMTP id 12so4383643bwz.13 for ; Wed, 14 Jul 2010 00:04:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:cc:subject :message-id:in-reply-to:references:reply-to:x-mailer:mime-version :content-type:content-transfer-encoding; bh=MCHAZE2org+M6fi0qDhlC08rCLxi2RUsfcm8nrHezFc=; b=ruQbSp4gfotw9dtNHfyrALwcMseBmVOkEri2/2AeNFFAnTCe+rKTlo4nQx86GgP5LD U1931GXORID+GQ1nJYElhXzjP/hiKwG1R9qnTDqzaoVH1UC/b8IwK/DpB9Fpyr7hIsWY m9tZXC3Ma5U7baKdpsSY6G9ewne4BQaiiF33c= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=date:from:to:cc:subject:message-id:in-reply-to:references:reply-to :x-mailer:mime-version:content-type:content-transfer-encoding; b=KIEe/nsju1J1oP+XbGD5SKrkvdcHIbEfHqd6yg88A4u3duEAORtMbC/DoNI5iOSWdG RtoZ84SuOiaNA2mvBoYIHJEPYDmAldOW8NzgP3x0v3QOOfgspZP1Lz7nbSnNbp06XkCU LeOPD7G3nz3FndiPab5NX2ffTMS9YB1CPIxW0= Received: by 10.204.81.146 with SMTP id x18mr5373183bkk.87.1279091097704; Wed, 14 Jul 2010 00:04:57 -0700 (PDT) Received: from ernst.jennejohn.org (p578E2E99.dip.t-dialin.net [87.142.46.153]) by mx.google.com with ESMTPS id y27sm30219844bkw.14.2010.07.14.00.04.55 (version=TLSv1/SSLv3 cipher=RC4-MD5); Wed, 14 Jul 2010 00:04:57 -0700 (PDT) Date: Wed, 14 Jul 2010 09:04:54 +0200 From: Gary Jennejohn To: Jerry Toung Message-ID: <20100714090454.1177b96b@ernst.jennejohn.org> In-Reply-To: References: X-Mailer: Claws Mail 3.7.5 (GTK+ 2.18.7; amd64-portbld-freebsd9.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org Subject: Re: disk I/O, VFS hirunningspace X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: gljennjohn@googlemail.com List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Jul 2010 07:04:59 -0000 On Tue, 13 Jul 2010 15:34:12 -0700 Jerry Toung wrote: > Hello List, > I am on 8.0 RELEASE amd64. My system has 2 RAID arrays connected to 2 > separate > controllers. > My I/O throughput tests jumped by ~100MB/sec on both channels, when I > commented out the > following piece of code from kern/vfs_bio.c > > void > waitrunningbufspace(void) > { > /* > mtx_lock(&rbreqlock); > while (runningbufspace > hirunningspace) { > ++runningbufreq; > msleep(&runningbufreq, &rbreqlock, PVM, "wdrain", 0); > } > mtx_unlock(&rbreqlock); > */ > } > > so far, I can't observe any side effects of not running it. Am I on a time > bomb? > Rather than commenting out the code try setting the sysctl vfs.hirunningspace to various powers-of-two. Default seems to be 1MB. I just changed it on the command line as a test to 2MB. You can do this in /etc/sysctl.conf. -- Gary Jennejohn