From owner-freebsd-stable@FreeBSD.ORG Sat Jan 9 14:28:13 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A0F871065672 for ; Sat, 9 Jan 2010 14:28:13 +0000 (UTC) (envelope-from alexander@leidinger.net) Received: from mail.ebusiness-leidinger.de (mail.ebusiness-leidinger.de [217.11.53.44]) by mx1.freebsd.org (Postfix) with ESMTP id 574118FC0C for ; Sat, 9 Jan 2010 14:28:13 +0000 (UTC) Received: from outgoing.leidinger.net (pD9E2E006.dip.t-dialin.net [217.226.224.6]) by mail.ebusiness-leidinger.de (Postfix) with ESMTPSA id 96614A15A; Sat, 9 Jan 2010 15:12:47 +0100 (CET) Received: from unknown (unknown [192.168.2.110]) by outgoing.leidinger.net (Postfix) with ESMTP id 5ACA52930CF; Sat, 9 Jan 2010 15:12:43 +0100 (CET) Date: Sat, 9 Jan 2010 15:12:40 +0100 From: Alexander Leidinger To: Jeremy Chadwick Message-ID: <20100109151240.0000282a@unknown> In-Reply-To: <20100108230506.GA7501@icarus.home.lan> References: <7346c5c61001030842r7dc76199y51e4c1c90a3eea6e@mail.gmail.com> <7346c5c61001080831w375d158fu5b1996ee58cb0f8d@mail.gmail.com> <20100108230506.GA7501@icarus.home.lan> X-Mailer: Claws Mail 3.7.2cvs15 (GTK+ 2.16.0; i586-pc-mingw32msvc) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-EBL-MailScanner-Information: Please contact the ISP for more information X-EBL-MailScanner-ID: 96614A15A.218D4 X-EBL-MailScanner: Found to be clean X-EBL-MailScanner-SpamCheck: not spam, spamhaus-ZEN, SpamAssassin (not cached, score=-1.44, required 6, autolearn=disabled, ALL_TRUSTED -1.44) X-EBL-MailScanner-From: alexander@leidinger.net X-EBL-MailScanner-Watermark: 1263651171.79623@TW2FqglLnwFDO9MOJ92OjA X-EBL-Spam-Status: No Cc: freebsd-stable@freebsd.org Subject: Re: ZFS performance degradation over time X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Jan 2010 14:28:13 -0000 On Fri, 8 Jan 2010 15:05:06 -0800 Jeremy Chadwick wrote: > All that said -- I know what the OP is referring to, as I've seen it > myself (on RELENG_7, and possibly early releases of 8.0). The only > way to relieve the pain, AFAIK, is to reboot. I assume the problem is that the memory handling in ZFS is not the best regarding memory fragmentation (at least in FreeBSD, I do not know of the memory handling in Solaris has a similar behavior). Regarding the RELENG_7 systems you have which use ZFS, are they SMP systems? If yes, do you see problems when a lot of parallel accesses (let's say several find in parallel) are made? All the commits to ZFS for 7-stable are triggered by a problem I have in this regard on a 7-stable system, but so far nothing helped. > I do see some MFC's done about 13 hours ago to RELENG_7 and RELENG_8 > that talk about the ARC and "paging pressure", which to me means > decreased performance when it occurs... or maybe it helps with the > kmem exhaustion problem? The brief description in the commit is > simply not enough to suffice; it's almost like we need a "FreeBSD ZFS > Newsletter" that documents what all the changes are that get > committed, what they fix, and what's being worked on/tested in HEAD > (for potential MFC). The change you talk about tells ZFS to cleanup the ARC when the max size is passed, instead when there is real need to get some free memory. The dresult is that the arc_max setting is more strictly followed, and that there is no expensive operation to be done to free the ARC when the system needs free memory. Bye, Alexander.