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[124.209.188.1]) by smtp.gmail.com with ESMTPSA id o8-20020a17090a3d4800b00233ebab3770sm1989594pjf.23.2023.02.25.20.41.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Feb 2023 20:41:02 -0800 (PST) Date: Sun, 26 Feb 2023 13:40:58 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , Yosry Ahmed , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv2 1/6] zsmalloc: remove insert_zspage() ->inuse optimization Message-ID: References: <20230223030451.543162-1-senozhatsky@chromium.org> <20230223030451.543162-2-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6E7FCA000A X-Stat-Signature: 4h137h5n6oyucut1csdjpw1pso56mw4t X-HE-Tag: 1677386464-462803 X-HE-Meta: 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 t48D6DNH L+2K32124ySxSjTyr1LvYqjGNoOEGcQ93kiEvjHrwzDBYREOBuhrL2cbX5elmEp4i4pwcH8gUZ7JN1cf5oHgV+mgvZygnwWVzVU8RpFLHXAu/eFYWuBzCDpaaGWZqVKpzRpX3Rt/0kdkmOmu4EUlvVeiPR4mwz2Vy0EsRAQEeml1J3WcRKjF3NDbWNeFaqJh7mdf8kaK6gFZLCNNkUnta/yrz6Wz5XXthbH2HbTWDUhgZpOgpgEcCuwRAqZBXkxkNwOvsnRe2mX976tRS8CFt0EAoA3ebLuxV1CGk3vuFzjnfGDz5RFxDOCsjciWTZUxMig98Twq/tjxHtr0hxg9+PvQnCfsA2wxiomYvBM0dUeCAdRS/sTCpPoR4yw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000885, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (23/02/23 15:09), Minchan Kim wrote: > > On Thu, Feb 23, 2023 at 12:04:46PM +0900, Sergey Senozhatsky wrote: > > This optimization has no effect. It only ensures that > > when a page was added to its corresponding fullness > > list, its "inuse" counter was higher or lower than the > > "inuse" counter of the page at the head of the list. > > The intention was to keep busy pages at the head, so > > they could be filled up and moved to the ZS_FULL > > fullness group more quickly. However, this doesn't work > > as the "inuse" counter of a page can be modified by > > zspage > > Let's use term zspage instead of page to prevent confusing. > > > obj_free() but the page may still belong to the same > > fullness list. So, fix_fullness_group() won't change > > Yes. I didn't expect it should be perfect from the beginning > but would help just little optimization. > > > the page's position in relation to the head's "inuse" > > counter, leading to a largely random order of pages > > within the fullness list. > > Good point. > > > > > For instance, consider a printout of the "inuse" > > counters of the first 10 pages in a class that holds > > 93 objects per zspage: > > > > ZS_ALMOST_EMPTY: 36 67 68 64 35 54 63 52 > > > > As we can see the page with the lowest "inuse" counter > > is actually the head of the fullness list. > > Let's write what the patch is doing cleary > > "So, let's remove the pointless optimization" or something better word. ACK to all feedback (for all the patches). Thanks!