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d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=eGczmUI3Q7tBDz6wgntLrYvORH2u57suFJN4sS9XHMg=; b=J3Kx2TuDW7eH6Jt5y0IC8U7Ba78D86xTxAXLh+j/1h0DQpvHjlyXb/0QVieEJisg2H et5nLjBy6xcQC/vWsKCXZOulrBIHCLWuaJt5zI5+oP5QGsTXVshW5uVzHR5TcZC1q7J4 1ancAxT7uJkL/IcJZEY6nVCO32vxWk6RWvyPxqymc24N+b7Cj1ZJKKYt9Xp8hZBtkTQx jFu2PliSAeKlMVTMPhLtzdWZF3B73De2rWTRAj906C0fh26ZLj1JvkPq0smbaI4epa73 mSP8zleR+VXFv7zloGtcSj/+3goFo8TiYAvxbrCGbaKyaowRgOwmUl30wHmfl9QKbQUL eEIA== X-Gm-Message-State: AOAM531bn//HY99ckeMOCeYNYRUHHvLTSrRT+2zWjzFCT+1n9LFl56EA j8S8al6n2HgEnAUkl15B4c8Xrpm0nvPvxDKwSPM= X-Google-Smtp-Source: ABdhPJwbGG+m1iJpnkK/yaEn5v01ZZS6w6rDZoUqckpzvyOrPJ0jn6fOZ/xNJwPWLiCPx3ok51fvY92/wFCVliHB1NI= X-Received: by 2002:a17:906:9b84:: with SMTP id dd4mr643814ejc.280.1638895829853; Tue, 07 Dec 2021 08:50:29 -0800 (PST) MIME-Version: 1.0 References: <1638619795-71451-1-git-send-email-wang.yong12@zte.com.cn> In-Reply-To: From: yong w Date: Wed, 8 Dec 2021 00:50:18 +0800 Message-ID: Subject: Re: [PATCH v2 linux-next] delayacct: track delays from memory compact To: Balbir Singh Cc: Andrew Morton , "Peter Zijlstra (Intel)" , mingo@kernel.org, LKML , Linux MM , yang.yang29@zte.com.cn, wang.yong12@zte.com.cn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5C86C1046302 X-Stat-Signature: jfhmpk1sk8riuzefpntjghkra9pr6phn Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=h+jSJvv4; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf31.hostedemail.com: domain of yongw.pur@gmail.com designates 209.85.208.41 as permitted sender) smtp.mailfrom=yongw.pur@gmail.com X-HE-Tag: 1638895831-610657 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: Balbir Singh =E4=BA=8E2021=E5=B9=B412=E6=9C=887=E6= =97=A5=E5=91=A8=E4=BA=8C 13:16=E5=86=99=E9=81=93=EF=BC=9A > > On Sun, Dec 05, 2021 at 07:08:02PM +0800, yong w wrote: > > Balbir Singh =E4=BA=8E2021=E5=B9=B412=E6=9C=885= =E6=97=A5=E5=91=A8=E6=97=A5 16:17=E5=86=99=E9=81=93=EF=BC=9A > > > > > > On Sat, Dec 04, 2021 at 04:09:55AM -0800, yongw.pur@gmail.com wrote: > > > > From: wangyong > > > > > > > > Delay accounting does not track the delay of memory compact. > > > > When there is not enough free memory, tasks can spend > > > > a amount of their time waiting for compact. > > > > > > > > To get the impact of tasks in direct memory compact, measure > > > > the delay when allocating memory through memory compact. > > > > > > > > > > Should we call this DIRECT_COMPACT and through documentation > > > or name change imply that this won't work for kcompactd the > > > kernel thread - based on my reading of the patches. > > > > > Using DIRECT_COMPACT is a little redundant=EF=BC=8Cbecause the > > delayacct stats of delay accounting is specific to tasks, it has > > nothing to do with kcompactd, which is similar to the RECLAIM field. > > > > What would we expect when we call delayacct -p > to be output? If the slow path of memory allocation is invoked in the kcompacd process, there may be delays being recorded. > Don't feel to strongly, but it can be confusing that kcompactd > has spent no time in compact'ing? Not that delayacct is used for > kernel threads, but I am not sure if that use case exists today. Yes, delayacct does not restrict the process of obtaining information=EF=BC= =8C but kcompactd is used for compaction, the compact delay of kcompatd is not actually a delay.Maybe it can be added to the document later to make it clearer. Thanks for your reply!