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[209.85.220.41]) by mx.google.com with SMTPS id s35sor20117513qtk.14.2019.05.13.21.37.16 for (Google Transport Security); Mon, 13 May 2019 21:37:16 -0700 (PDT) Received-SPF: pass (google.com: domain of shy828301@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=lBg4mAX3; spf=pass (google.com: domain of shy828301@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Tf3korJmRLD8o2Lf06LrqOczw1F6ZM2FyAdskXAP/yk=; b=lBg4mAX3TS8PJBOsb+445RvCKsl4l9r5dT0BTkb/FL86zuZPgzqK0IYwRDoq8DS/wW bkN3AEQUlfMHlZU+0IVgdRfgFaOm6ajkuDV2FOR1rhtOAcMcbR1RfK+japxmOfw3PGr1 1KkIg29RCtaWyEWi81wAsuTrGj7UFXSekgkO7QlV3qE02GyWhbmyKqhRfqgs+DR/k+CO xdanmaGLWE6F7ApSxivM8U+T/V/mz9LNfgVXI9ujMA77bvmfSG2ZBWbf2GcKqwClQ0Rj UHVn5SVbESeu1MTDsvNW1+ztooPYlK9Aop1IqrJ7HASDwOGZcC5O3Ly+tDFg9XW9YDEa 2uaw== X-Google-Smtp-Source: APXvYqwh4a0o8vAEeDVZY6kolyij7RZoaYa1MYOibq43kvFPp4BJjJKs9M6IS2Pmf3oMCR3z5OP/uvmiygdphi38f9o= X-Received: by 2002:ac8:5409:: with SMTP id b9mr27316238qtq.326.1557808635902; Mon, 13 May 2019 21:37:15 -0700 (PDT) MIME-Version: 1.0 References: <1557505420-21809-1-git-send-email-yang.shi@linux.alibaba.com> <20190513080929.GC24036@dhcp22.suse.cz> <20190513214503.GB25356@dhcp22.suse.cz> In-Reply-To: <20190513214503.GB25356@dhcp22.suse.cz> From: Yang Shi Date: Mon, 13 May 2019 21:36:59 -0700 Message-ID: Subject: Re: [v2 PATCH] mm: vmscan: correct nr_reclaimed for THP To: Michal Hocko Cc: Yang Shi , Huang Ying , Johannes Weiner , Mel Gorman , kirill.shutemov@linux.intel.com, Hugh Dickins , Shakeel Butt , william.kucharski@oracle.com, Andrew Morton , Linux MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" 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 Mon, May 13, 2019 at 2:45 PM Michal Hocko wrote: > > On Mon 13-05-19 14:09:59, Yang Shi wrote: > [...] > > I think we can just account 512 base pages for nr_scanned for > > isolate_lru_pages() to make the counters sane since PGSCAN_KSWAPD/DIRECT > > just use it. > > > > And, sc->nr_scanned should be accounted as 512 base pages too otherwise we > > may have nr_scanned < nr_to_reclaim all the time to result in false-negative > > for priority raise and something else wrong (e.g. wrong vmpressure). > > Be careful. nr_scanned is used as a pressure indicator to slab shrinking > AFAIR. Maybe this is ok but it really begs for much more explaining I don't know why my company mailbox didn't receive this email, so I replied with my personal email. It is not used to double slab pressure any more since commit 9092c71bb724 ("mm: use sc->priority for slab shrink targets"). It uses sc->priority to determine the pressure for slab shrinking now. So, I think we can just remove that "double slab pressure" code. It is not used actually and looks confusing now. Actually, the "double slab pressure" does something opposite. The extra inc to sc->nr_scanned just prevents from raising sc->priority. > than "it should be fine". This should have happened when THP swap out > was implemented... > > -- > Michal Hocko > SUSE Labs >