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[2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with ESMTPSA id x12-20020ae9f80c000000b0078a35fc488bsm268911qkh.52.2024.04.04.19.35.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Apr 2024 19:35:19 -0700 (PDT) Date: Thu, 4 Apr 2024 22:35:18 -0400 From: Johannes Weiner To: Yosry Ahmed Cc: Andrew Morton , Nhat Pham , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 4/5] mm: zswap: remove same_filled module params Message-ID: <20240405023518.GD641486@cmpxchg.org> References: <20240405013547.1859126-1-yosryahmed@google.com> <20240405013547.1859126-5-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240405013547.1859126-5-yosryahmed@google.com> X-Rspamd-Queue-Id: 464A0C000D X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: jyq9qbkngj5bz9xoyrqjbanih5ofiegg X-HE-Tag: 1712284520-627329 X-HE-Meta: U2FsdGVkX1+1sXh+ZYBCeSArJ3dfdbGTBYQ4wUvw+qak1WpHaP8hoIYWFrpkFQ2WEhz4tMwgeh4k8bSZBTZE3ymT3e4LsZJVzWgQfATbVn7gLjG8LzRMvTPwOeoLy5hsxEl9De8+0j+zH9y5lEPbk4hQgJp3+ohBqZaPyhFAAJxn7VJNnf4UavEYasXGTU9vY0geAdZSFjM26UgA2Y7xFRHwn4qam5QS3X7dqqkmrAQXW+N2jge2tlRtvPgnPeP7bo2r41NxB0sTErJm3AIgNgIn/JHM6X9RQSOF7xLvdpTYy++1JDPdjhJLbasXxv/xesilUogyXvUiwILT/KEotrUQwNLMW22iwi1dIWmWPYUYfaRxZpPEoG7J/c1ZYU6oNIendxjMFrZc+qIP0eVcQvieUXlPOMLMWuwPVr+AiKt2eTm/BuV0XFWTXSneHAH7k1WzRfQ2SiS9W+Bv+CDUtYL0jONKsHsMNbewBWkCRMHv/DLkE1rV7qNX0WosbaolZ5emLX2x/3xM3jN0LDUKq9ZNpz6t3YroB0Zc1hdUaKR4TclLI6D+4anzqElJVgcRikEoYY93RuTTLQQGa4G5GiviKai0hcnpN/CPuegr1SQRChY9TUAUaGPr4XGv+CkzvFIGX++HvZMytsxwmu76VmQa279QP7i0YIcXzxqtixVx3BCNQA8lQeyb/VNGPpnMrgJ0l9PcdDch9RU009zt47UeRS1f1N9/jTLBt0MseDbpzhW46ItODBq5ZIkIdi1/C4Wuz56dEFHBU00cn4rw4POLAOPOgKjOopsBewhdm0K5aULsEUScAIfs7MkCu0Sqbqae4FKviqEGyrK0cLxyCct+jo+t9Y5q1o6ekDk1C4jG9LIMWWh7DmeblISqHL4ur0rXw/JAksw5IAZ7JuKVOj+xzZ75JmlIH5EG9QtqrNXxxSL5QRAwBy732qDbUB6WISxehkmMXUQFOejo9us HW9qKbyK 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 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: List-Subscribe: List-Unsubscribe: On Fri, Apr 05, 2024 at 01:35:46AM +0000, Yosry Ahmed wrote: > These knobs offer more fine-grained control to userspace than needed and > directly expose/influence kernel implementation; remove them. > > For disabling same_filled handling, there is no logical reason to refuse > storing same-filled pages more efficiently and opt for compression. > Scanning pages for patterns may be an argument, but the page contents > will be read into the CPU cache anyway during compression. Also, > removing the same_filled handling code does not move the needle > significantly in terms of performance anyway [1]. > > For disabling non_same_filled handling, it was added when the compressed > pages in zswap were not being properly charged to memcgs, as workloads > could escape the accounting with compression [2]. This is no longer the > case after commit f4840ccfca25 ("zswap: memcg accounting"), and using > zswap without compression does not make much sense. > > [1]https://lore.kernel.org/lkml/CAJD7tkaySFP2hBQw4pnZHJJwe3bMdjJ1t9VC2VJd=khn1_TXvA@mail.gmail.com/ > [2]https://lore.kernel.org/lkml/19d5cdee-2868-41bd-83d5-6da75d72e940@maciej.szmigiero.name/ > > Signed-off-by: Yosry Ahmed Acked-by: Johannes Weiner