From owner-freebsd-fs@freebsd.org Mon Aug 27 14:19:18 2018 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B788A108B619 for ; Mon, 27 Aug 2018 14:19:18 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from onlyone.not-for.work (onlyone.not-for.work [IPv6:2a01:4f8:201:6350::2]) by mx1.freebsd.org (Postfix) with ESMTP id 4446B72591 for ; Mon, 27 Aug 2018 14:19:18 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from [192.168.23.186] (unknown [89.113.128.32]) (Authenticated sender: lev@serebryakov.spb.ru) by onlyone.not-for.work (Postfix) with ESMTPSA id 53632F01; Mon, 27 Aug 2018 17:19:11 +0300 (MSK) Reply-To: lev@FreeBSD.org Subject: Re: ZFS (ARC) performance regression in r321610 To: Yamagi Burmeister , freebsd-fs@freebsd.org Cc: MacCrest@gmail.com References: <20180827154727.80f92fff9bbc931b37928d43@yamagi.org> From: Lev Serebryakov Openpgp: preference=signencrypt Autocrypt: addr=lev@FreeBSD.org; 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WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180827154727.80f92fff9bbc931b37928d43@yamagi.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Aug 2018 14:19:18 -0000 On 27.08.2018 16:47, Yamagi Burmeister wrote: > With this program I was able to bisect the source and identify commit > r321610 (MFV r318946: 8021 ARC buf data scatter-ization) as the culprit: > https://svnweb.freebsd.org/base?view=revision&revision=321610 You could try to set "zfs_abd_scatter_enabled = 0" via kgdb and repeat tests to be sure, that this code is a problem. BTW, it is not clear, that FreeBSD needs this at all. -- // Lev Serebryakov