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b=VgP6OtxwBwDzr791/Nt6+RR29bRcLtrHBxabxtJcpOrvfFJxEp1E0Yro5jTduLzL6F I6AbVUNpkr1eLO6CM1fwIcjDacdJ8FELp5i3QPb3C2P0IDlijFX/A2zSxCI0VyJDkkUI 2A+IXW7K9xD34m/WZMYg+WEwAv0gYLEdYpKdY4WbKyJGxbzRzx8pNZ5qe4KLF8gRvgEP F6XYct9g34L8vTYOEjMYK6D61DXTtNxRc0j3tcLtqFu9hFjifedYTS/90wrlS6fU+osK qBeQVyWYez4cfouOb/IAlw5AoWScbYyD1w2+t2ZKExAWL8UZaknSvfyff5NGcvhR5yFx psyg== X-Gm-Message-State: AOAM5306TrUzNS+wyx3GGL9iLGeQO9pIqV7mDpTlqmSlfjJdgF2kylVd Az5LeZ5cPi5KOK/lG4xBQzEUXg== X-Google-Smtp-Source: ABdhPJwo2whi0Lw6fIE7bFveFIZ4RGr/nKwjHmSonYZXWPvKeNeMwgJAgIEpaK/ZZTq1giywqo1Sfw== X-Received: by 2002:a05:6402:1383:: with SMTP id b3mr5999967edv.100.1607597374154; Thu, 10 Dec 2020 02:49:34 -0800 (PST) Received: from localhost ([163.114.131.1]) by smtp.gmail.com with ESMTPSA id bo20sm4545634edb.1.2020.12.10.02.49.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Dec 2020 02:49:33 -0800 (PST) Date: Thu, 10 Dec 2020 05:47:26 -0500 From: Johannes Weiner To: Yu Zhao Cc: Andrew Morton , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org Subject: Re: [PATCH] mm: don't SetPageWorkingset unconditionally during swapin Message-ID: <20201210104726.GA264602@cmpxchg.org> References: <20201209012400.1771150-1-yuzhao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201209012400.1771150-1-yuzhao@google.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Dec 08, 2020 at 06:24:00PM -0700, Yu Zhao wrote: > We are capable of SetPageWorkingset based on refault distances after > commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU") > This is done by workingset_refault(), which is right above the > unconditional SetPageWorkingset deleted by this patch. > > The unconditional SetPageWorkingset miscategorizes pages that are > read ahead or never belonged to the working set (e.g., tmpfs pages > accessed by fd). When those pages are swapped in (after they were > swapped out) for the first time, they skew PSI (when using > async swap). When this happens again, depending on their refault > distances, they might skew workingset_restore_anon counter in > addition to PSI because their shadows say they were part of the > working set. > > Signed-off-by: Yu Zhao Acked-by: Johannes Weiner