From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37871C433E0 for ; Wed, 24 Jun 2020 03:56:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F14492070E for ; Wed, 24 Jun 2020 03:56:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F14492070E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9B69F6B0002; Tue, 23 Jun 2020 23:56:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9678D6B0003; Tue, 23 Jun 2020 23:56:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A4356B0007; Tue, 23 Jun 2020 23:56:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 72BA56B0002 for ; Tue, 23 Jun 2020 23:56:29 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 35A918248068 for ; Wed, 24 Jun 2020 03:56:29 +0000 (UTC) X-FDA: 76962743298.27.dirt02_05077dd26e41 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id F2DB83D668 for ; Wed, 24 Jun 2020 03:56:28 +0000 (UTC) X-HE-Tag: dirt02_05077dd26e41 X-Filterd-Recvd-Size: 3897 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Wed, 24 Jun 2020 03:56:27 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0U0YpXZ6_1592970982; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U0YpXZ6_1592970982) by smtp.aliyun-inc.com(127.0.0.1); Wed, 24 Jun 2020 11:56:22 +0800 Date: Wed, 24 Jun 2020 11:56:22 +0800 From: Wei Yang To: Baoquan He Cc: Wei Yang , Dan Williams , Andrew Morton , Oscar Salvador , Linux MM , Linux Kernel Mailing List , David Hildenbrand Subject: Re: [PATCH] mm/spase: never partially remove memmap for early section Message-ID: <20200624035622.GA10774@L-31X9LVDL-1304.local> Reply-To: Wei Yang References: <20200623094258.6705-1-richard.weiyang@linux.alibaba.com> <20200624014737.GG3346@MiWiFi-R3L-srv> <20200624034638.GA10687@L-31X9LVDL-1304.local> <20200624035236.GI3346@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624035236.GI3346@MiWiFi-R3L-srv> X-Rspamd-Queue-Id: F2DB83D668 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 24, 2020 at 11:52:36AM +0800, Baoquan He wrote: >On 06/24/20 at 11:46am, Wei Yang wrote: >> On Wed, Jun 24, 2020 at 09:47:37AM +0800, Baoquan He wrote: >> >On 06/23/20 at 05:21pm, Dan Williams wrote: >> >> On Tue, Jun 23, 2020 at 2:43 AM Wei Yang >> >> wrote: >> >> > >> >> > For early sections, we assumes its memmap will never be partially >> >> > removed. But current behavior breaks this. >> >> >> >> Where do we assume that? >> >> >> >> The primary use case for this was mapping pmem that collides with >> >> System-RAM in the same 128MB section. That collision will certainly be >> >> depopulated on-demand depending on the state of the pmem device. So, >> >> I'm not understanding the problem or the benefit of this change. >> > >> >I was also confused when review this patch, the patch log is a little >> >short and simple. From the current code, with SPARSE_VMEMMAP enabled, we >> >do build memmap for the whole memory section during boot, even though >> >some of them may be partially populated. We just mark the subsection map >> >for present pages. >> > >> >Later, if pmem device is mapped into the partially boot memory section, >> >we just fill the relevant subsection map, do return directly, w/o building >> >the memmap for it, in section_activate(). Because the memmap for the >> >unpresent RAM part have been there. I guess this is what Wei is trying to >> >do to keep the behaviour be consistent for pmem device adding, or >> >pmem device removing and later adding again. >> > >> >Please correct me if I am wrong. >> >> You are right here. >> >> > >> >To me, fixing it looks good. But a clear doc or code comment is >> >necessary so that people can understand the code with less time. >> >Leaving it as is doesn't cause harm. I personally tend to choose >> >the former. >> > >> >> The former is to add a clear doc? > >Sorry for the confusion. The former means the fix in your patch. Maybe a >improved log and some code comment adding can make it more perfect. > Sure, I would try to add more log and comments, in case you have some good suggestion, just let me know :) -- Wei Yang Help you, Help me