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AJvYcCVleDHWAQVTRc/WrNzY/1FbqF8j6H8qR+MFZEZWVI//oAUBNayR/RY7sk6NDrvJnS7Ra4w1eOKk8zJkmGToMK0MDfY= X-Gm-Message-State: AOJu0YxlaiuI2w9n0iee7psssl89gG/KpStx+uRbhuz78IPgDZ7wPzyn njvhdbMpAsarLcP/RRd7ALsVRAypcYksYs9TASVOzs9vfJY54V3MGntxGkZVBb0afm4+FOKjsLZ Z7f3dNb8zw9/LzoDQCTTwy8XZF74= X-Google-Smtp-Source: AGHT+IEeYXo30v/uUKaZSV4Ao9ZFszwL1iUhnFTkv6dJ2veewp9UyjVuTTzOuMAQusYtnQNdVXBq+TRUse1qHD8ldq4= X-Received: by 2002:a05:6358:a096:b0:1ab:e07d:c93c with SMTP id e5c5f4694b2df-1adb242e352mr1488786355d.4.1722375653955; Tue, 30 Jul 2024 14:40:53 -0700 (PDT) MIME-Version: 1.0 References: <20240725232813.2260665-1-nphamcs@gmail.com> <20240725232813.2260665-2-nphamcs@gmail.com> <20240730033929.GB2866591@cmpxchg.org> In-Reply-To: From: Nhat Pham Date: Tue, 30 Jul 2024 14:40:42 -0700 Message-ID: Subject: Re: [PATCH 1/2] zswap: implement a second chance algorithm for dynamic zswap shrinker To: Yosry Ahmed Cc: Johannes Weiner , akpm@linux-foundation.org, shakeelb@google.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, flintglass@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2FACB40011 X-Stat-Signature: u7pae3rb7nishjit39g918cdtcrmmg51 X-Rspam-User: X-HE-Tag: 1722375655-155376 X-HE-Meta: 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 IGMhU5WY taEnwKZVY5oT1R345Wr6rjmC2oR++1czQDMuR+9FlnFb0oGyD6QFgk8OEV5Rhm5vd960XoOj0AYol/50S3Og+XwpO1Pu5rlz0LojMe7nmCKHIYOagyFJ81gPYTruKlPo8eEI1okKQ2D8fCdARKonBFSbYjoDYg0CuzB23CLkQvXTIJFq4pxmVJy6LauDAtf39WyEHcYP/jVPkK8k3A02HPstOIiZcJdlBRcwJIuzJqK7L0s1bg7EB+gSnEnh6aeIILcz5S+m6oed0eVwPzSUqtmZnxBY4J+vMSJaXVpKCzDafYE79o7cTlvcNzp+2uqP3xFY+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000431, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 30, 2024 at 11:46=E2=80=AFAM Yosry Ahmed wrote: > > > I still think the nr_deferred handling in the shrinker framework does > not seem compatible with zswap. Entries could be double counted, and > previously counted entries could go away during swapins. Unless I am > missing something, it seems like the scanning can be arbitrary, and > not truly proportional to the reclaim priority and zswap LRUs size. We can do some investigation by the side. I did find the trace point that collects deferred numbers, maybe that can illustrate the problem? It'd be an orthogonal issue though. I don't think fixing the nr_deferred part would be enough to handle the various cases Johannes pointed out.