From owner-freebsd-fs@FreeBSD.ORG Wed Feb 15 15:39:47 2012 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 23E54106564A for ; Wed, 15 Feb 2012 15:39:47 +0000 (UTC) (envelope-from gkontos.mail@gmail.com) Received: from mail-iy0-f182.google.com (mail-iy0-f182.google.com [209.85.210.182]) by mx1.freebsd.org (Postfix) with ESMTP id E13228FC16 for ; Wed, 15 Feb 2012 15:39:46 +0000 (UTC) Received: by iaeo4 with SMTP id o4so2073641iae.13 for ; Wed, 15 Feb 2012 07:39:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=hqkRYkUmO3CPFWofk0zwuNPCxqdshEGoqCi6FiP7Mcs=; b=OoinEsVPk/q1sOjJ81zzKGayN5fH9MXkSVbuPGc7IjTs3sP5z5rlFGji8id7jBazqL nq6ayTp4T4U5SssFu/GTiiUnE+z3mo3ZK/OS5IQpvXK0HmtEAxOX057S8uoEFYv1kAmA l2vVZHLLyIQ+YFWhwbP6KU1PzxGw+L06PDFh8= MIME-Version: 1.0 Received: by 10.43.126.67 with SMTP id gv3mr1559964icc.50.1329320385730; Wed, 15 Feb 2012 07:39:45 -0800 (PST) Received: by 10.231.231.17 with HTTP; Wed, 15 Feb 2012 07:39:45 -0800 (PST) In-Reply-To: <41082.1329320114.6955040073494560768@ffe1.ukr.net> References: <70229.1329318412.9319724204137054208@ffe16.ukr.net> <41082.1329320114.6955040073494560768@ffe1.ukr.net> Date: Wed, 15 Feb 2012 17:39:45 +0200 Message-ID: From: George Kontostanos To: Pavlo Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-fs@freebsd.org Subject: Re: ZFS and mem management 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: Wed, 15 Feb 2012 15:39:47 -0000 2012/2/15 Pavlo : > > > 2012/2/15 Pavlo : >> >> >> >>>On 15/02/2012 13:39, Pavlo wrote: >>>> >> >>>> >> >> Unfortunately we can't afford disabling prefetch. It is too much >>>> >> >> of an>> overhead.>> >> Also I made some tests. I have process that maps file >>>> >> >> using mmap() and>> writes or reads first byte of each page of mapped file >>>> >> >> with some data.> >>>Note that ZFS is designed so that it interacts somewhat badly with >>>mmap() and other kernel services which rely on coherency between VM and >>>IO such as sendfile(). At the very best, you will have two in-kernel >>>copies of all data buffers used with such interfaces, but there have >>>been sporadic reports that there are other bugs with it. >>> >>>If you have a test server, I'd recommend you do the same test on UFS for >>>comparison. >> >> Was going to try this... Thanks for reply. >> _______________________________________________ >> freebsd-fs@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-fs >> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > > Why do you think that disabling prefetch is an overhead? > > > -- > George Kontostanos > Aicom telecoms ltd > http://www.aisecure.net > > > > Well... not me though. System administrator >_> . I suppose because we have > a big IO traffic. Not for a highly random I/O environment. -- George Kontostanos Aicom telecoms ltd http://www.aisecure.net