From owner-freebsd-fs@FreeBSD.ORG Mon Oct 28 18:14:34 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 3B07EADB; Mon, 28 Oct 2013 18:14:34 +0000 (UTC) (envelope-from slw@zxy.spb.ru) Received: from zxy.spb.ru (zxy.spb.ru [195.70.199.98]) by mx1.freebsd.org (Postfix) with ESMTP id ED389226C; Mon, 28 Oct 2013 18:14:33 +0000 (UTC) Received: from slw by zxy.spb.ru with local (Exim 4.69 (FreeBSD)) (envelope-from ) id 1VarMd-000I4J-NG; Mon, 28 Oct 2013 22:16:31 +0400 Date: Mon, 28 Oct 2013 22:16:31 +0400 From: Slawa Olhovchenkov To: aurfalien Subject: Re: ZFS txg implementation flaw Message-ID: <20131028181631.GV63359@zxy.spb.ru> References: <20131028092844.GA24997@zxy.spb.ru> <0F1D571E-2806-4392-A5EC-BE66A3C92BF7@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0F1D571E-2806-4392-A5EC-BE66A3C92BF7@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: slw@zxy.spb.ru X-SA-Exim-Scanned: No (on zxy.spb.ru); SAEximRunCond expanded to false Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Oct 2013 18:14:34 -0000 On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > > On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > > > I can be wrong. > > As I see ZFS cretate seperate thread for earch txg writing. > > Also for writing to L2ARC. > > As result -- up to several thousands threads created and destoyed per > > second. And hundreds thousands page allocations, zeroing, maping > > unmaping and freeing per seconds. Very high overhead. > > > > In systat -vmstat I see totfr up to 600000, prcfr up to 200000. > > > > Estimated overhead -- 30% of system time. > > > > Can anybody implement thread and page pool for txg? > > Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? vfs.zfs.txg.timeout: 5 Only x5 lowering (less in real case with burst writing). And more fragmentation on writing and etc.