From owner-freebsd-current@FreeBSD.ORG Mon Oct 28 18:27:58 2013 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id D3E6DA5B for ; Mon, 28 Oct 2013 18:27:58 +0000 (UTC) (envelope-from freebsd@allanjude.com) Received: from mx1.scaleengine.net (beauharnois2.bhs1.scaleengine.net [142.4.218.15]) by mx1.freebsd.org (Postfix) with ESMTP id B07702379 for ; Mon, 28 Oct 2013 18:27:57 +0000 (UTC) Received: from [10.1.1.1] (S01060001abad1dea.hm.shawcable.net [50.70.108.129]) (Authenticated sender: allan.jude@scaleengine.com) by mx1.scaleengine.net (Postfix) with ESMTPSA id D218C428CA for ; Mon, 28 Oct 2013 18:27:56 +0000 (UTC) Message-ID: <526EACB4.9030906@allanjude.com> Date: Mon, 28 Oct 2013 14:28:04 -0400 From: Allan Jude User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: freebsd-current@freebsd.org Subject: Re: ZFS txg implementation flaw References: <20131028092844.GA24997@zxy.spb.ru> <0F1D571E-2806-4392-A5EC-BE66A3C92BF7@gmail.com> <20131028181631.GV63359@zxy.spb.ru> In-Reply-To: <20131028181631.GV63359@zxy.spb.ru> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Oct 2013 18:27:58 -0000 On 2013-10-28 14:16, Slawa Olhovchenkov wrote: > 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. > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >From my understanding, increasing the timeout so you are doing fewer transaction groups, would actually be the way to increase performance, at the cost of 'bursty' writing and the associated uneven latency. -- Allan Jude