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Thu, 06 Feb 2025 04:26:59 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:28ab:cea4:aa8a:127a]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21f3653c9a2sm11470325ad.77.2025.02.06.04.26.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Feb 2025 04:26:59 -0800 (PST) Date: Thu, 6 Feb 2025 21:26:54 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Sergey Senozhatsky , Kairui Song , Andrew Morton , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv4 02/17] zram: do not use per-CPU compression streams Message-ID: References: <20250131090658.3386285-1-senozhatsky@chromium.org> <20250131090658.3386285-3-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 165BEA0032 X-Stat-Signature: uutddb8p8i6fnrcxeezk6k9twdpzjmh5 X-Rspam-User: X-HE-Tag: 1738844820-564326 X-HE-Meta: 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 fi75yky/ 5nD87trjvh0b2ej0+9achyAxhrK26rBrcVswLaGMGQ7Tyhk5+NlfCBcBwOqwFcUJTsbwEK2FFCBrBuFZbU1mT1nu4ayJZ05qDCEAWiwpwTG4BQjzl/lMs6Njh9NIUSdbPMXtVBLRTUoxTDEh/QJZ97ddmZ82B9wItqmLjq7hJtjj2gNqd9j4zn23uaTrh/Wei/XfvCAfqpqHFcpZYqHcNPUguPMlj81KVe1R4hP03QZYm8vWOFNY4fhIM6mtHUjoUEErW7pLn6cxiviGaqX3VLyfvrgMH//O31Z4md9RF3Y62q74nu0CDnWr3WlIhvOsGTCVp9k/103AZq/rwKXbbDYpUEc/YDCccab7T2Aqqk9sMjkE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.004661, 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 (25/02/03 21:00), Yosry Ahmed wrote: > On Mon, Feb 03, 2025 at 12:49:42PM +0900, Sergey Senozhatsky wrote: > > On (25/02/01 17:21), Kairui Song wrote: > FWIW, I am not familiar at all with the zram code but zswap uses per-CPU > acomp contexts with a mutex instead of a spinlock. So the task uses the > context of the CPU that it started on, but it can be preempted or > migrated and end up running on a different CPU. Thank you for the idea. We couldn't do that before (in zram), in a number of cases per-CPU stream was taken from atomic context (under zram table entry spinlock/bit-spinlock), but it's possible now because entry lock is preemptible.