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Mon, 10 Oct 2022 19:31:14 -0700 (PDT) From: xu xin X-Google-Original-From: xu xin To: imbrenda@linux.ibm.com Cc: akpm@linux-foundation.org, david@redhat.com, jiang.xuexin@zte.com.cn, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ran.xiaokai@zte.com.cn, xu.xin.sc@gmail.com, xu.xin16@zte.com.cn, yang.yang29@zte.com.cn Subject: Re: [PATCH v2 0/5] ksm: support tracking KSM-placed zero-pages Date: Tue, 11 Oct 2022 02:31:09 +0000 Message-Id: <20221011023109.322501-1-xu.xin16@zte.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221010154248.1ee86294@p-imbrenda> References: <20221010154248.1ee86294@p-imbrenda> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665455476; a=rsa-sha256; cv=none; b=TY9XRJoj629593VheNXRm0IB6YzROc8Wr3UTt0fdxz1eCkVNioLrZJoUWX0f3QGfkAZjR1 pxYbkYXX570Ysp5afvy+AU3YfogyqPiH/XukiJ6UF4vkVFVDXRuli02Gz8VFWKAFfl9B5N 4gETjHYx9GhzETZG+tP23Sv854xuVyk= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=mr1k+gWl; 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dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: i3bhkagpprhm1auij3b4p1gfoakna1ii X-Rspamd-Queue-Id: CDEEA120026 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1665455476-430451 X-Bogosity: Ham, tests=bogofilter, spamicity=0.077312, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > >> Hello, Thanks for your reply. >> >> > >> >why are you trying so hard to fix something that is not broken? >> >> Actually, it breaks the definition of unmerge, though it's usually not a big >> problem. >> > >> >can't you just avoid using use_zero_pages? >> >> use_zero_pages is good, not just because of cache colouring as described in doc, >> but also because use_zero_pages can accelerate merging empty pages when there >> are plenty of empty pages (full of zeros) as the time of page-by-page comparision >> (unstable_tree_search_insert) is saved. > >interesting, this is some useful information that you could have written >in the cover letter and/or commit messages, to explain why you are >proposing these changes :) Yes. I have done it in v3. Thanks. > >> >> > >> >why is it so important to know how many zero pages have been merged? >> >and why do you want to unmerge them? >> >> Zero pages may be the most common merged pages in actual environment(not only VM but > >also interesting information, which you could also have written in the >cover letter and/or commit messages > >> also including other application like containers). Sometimes customers (app developers) >> are very interested in how many non-zero-pages are actually merged in their apps. >> >> > >> >the important thing is that the sysadmin knows how much memory would be >> >needed to do the unmerge, and that information is already there. >> > >> >> I think it's about chicken-and-egg problem. >> >> >> Anyway, thanks for your reply. >>