From owner-freebsd-fs@FreeBSD.ORG Tue Sep 13 09:56:43 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E52DE1065670 for ; Tue, 13 Sep 2011 09:56:43 +0000 (UTC) (envelope-from szoftos@freemail.hu) Received: from fmx21.freemail.hu (fmx21.freemail.hu [195.228.245.71]) by mx1.freebsd.org (Postfix) with SMTP id 31DC48FC08 for ; Tue, 13 Sep 2011 09:56:42 +0000 (UTC) Received: (qmail 45534 invoked from network); 13 Sep 2011 11:56:41 +0200 Received: from 195.228.245.211 (HELO localhost) (91.82.87.114) by fmx21.freemail.hu with SMTP; 13 Sep 2011 11:56:41 +0200 Date: Tue, 13 Sep 2011 11:56:41 +0200 (CEST) From: Laszlo KAROLYI To: freebsd-fs In-Reply-To: Message-ID: X-Originating-IP: [91.82.87.114] X-HTTP-User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:5.0) Gecko/20100101 Firefox/5.0 MIME-Version: 1.0 Content-Type: TEXT/plain; CHARSET=ISO-8859-2 Content-Transfer-Encoding: QUOTED-PRINTABLE Subject: Re: ZFS-lighttpd2-sendfile, too high IO X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Sep 2011 09:56:44 -0000 Hello,=0A=0Ait seems that turning off sendfile() in lighttpd2 completely so= lved my problem.=0A=0AThe inactive memory usage ceased, wired memory raised= for ARC cache, and I see an enormous fall of IO load under the same (or ev= en higher) network load. The disk IO load now scales to the network load.= =0A=0ASomething must be not right with the sendfile support in ZFS.=0A=0AHo= wever, my problem solved, and I'd suggest turning off sendfile in any progr= ams in the future, unless this bug gets fixed.=0A=0ALaszlo=0A=0ABob Friesen= hahn =EDrta:=0A>On Mon, 12 Sep 2011, Laszlo = KAROLYI wrote:=0A>=0A>> But does this explain the 4-5mbyte/s reads when hav= ing a 15mbit/s network load?=0A>=0A>There are only two viable explanations:= =0A>=0A> o Insuffient caching due to insufficient resources=0A>=0A> o D= ata is not being cached at all=0A>=0A>Zfs reads whole 128K blocks (or whate= ver the filesystem blocksize is) =0A>at a time. It does not read partial b= locks from underlying storage. =0A>This makes it very expensive to perform = many small read accesses if =0A>the reads are not subsequently cached in th= e ARC.=0A>=0A>Bob=0A>-- =0A>Bob Friesenhahn=0A>bfriesen@simple.dallas.tx.us= , http://www.simplesystems.org/users/bfriesen/=0A>GraphicsMagick Maintainer= , http://www.GraphicsMagick.org/=0A