From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758500AbdLRL43 (ORCPT ); Mon, 18 Dec 2017 06:56:29 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:11954 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758363AbdLRL41 (ORCPT ); Mon, 18 Dec 2017 06:56:27 -0500 From: Chao Yu Subject: Re: [PATCH v4] f2fs: obsolete free nid list approach To: Jaegeuk Kim CC: , , References: <20171130113112.50058-1-yuchao0@huawei.com> <20171201073637.GC86192@jaegeuk-macbookpro.roam.corp.google.com> <2cb36fd5-462d-d415-5f0c-871272480813@huawei.com> <20171214192156.GA35234@jaegeuk-macbookpro.roam.corp.google.com> Message-ID: Date: Mon, 18 Dec 2017 19:56:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20171214192156.GA35234@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A010202.5A37ACDC.0027,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: d4c90dc0d065b0f18aa1045ca091c60d Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017/12/15 3:21, Jaegeuk Kim wrote: > On 12/11, Chao Yu wrote: >> Hi Jaegeuk, >> >> On 2017/12/1 15:36, Jaegeuk Kim wrote: >>> Hi Chao, >>> >>> This is really hard to review and risky a lot to apply it shortly. Do we have a >> >> I can understand your concern. >> >>> strong reason we have to do this? The original design goal was to minimize >>> allocation delay which is almost zero for now. Of course, I agreed that there'd >> >> I agreed, For nid allocation performance there will be no room to improve since >> we have already used memory to exchange performance there. >> >> After applying this patch, I can encounter slight regression in scenario of >> continuous file creation. >> >> Anyway, goal of this patch is not aiming at performance, instead, it intends to >> reduce code complexity, and maybe, slightly improving performance of allocation >> in low-memory environment. So actually, this is a trade-off problem. >> >> If we decide to use old approach, I think what can be improved is that if we run >> out-of-memory, we can switch to nid bitmap searching in alloc_nid rather than >> preloading free nid entry in build_free_nid whose performance is memory sensitive. >> Thoughts? > > Hmm, in terms of performance, do we really suffer from memory pressure when > preloading free nids? Sorry for late reply, I'm on trip now. I guess it will, let me emulate low memory environment, and do intensive allocation test, will report to you if there is any progress. Thanks,