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Tue, 20 Oct 2026 21:56:21 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:97d1:a8be:236d:bf79]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3673e153519sm3617931eec.3.2026.10.20.21.56.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 21:56:20 -0700 (PDT) Date: Wed, 21 Oct 2026 13:56:17 +0900 From: Sergey Senozhatsky To: Hillf Danton Cc: Sergey Senozhatsky , Andrew Morton , Brian Geffon , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v6 09/13] zram: split zcomp into separate R/W streams Message-ID: References: <20261021024236.1787884-10-senozhatsky@chromium.org> <20261021042350.907-1-hdanton@sina.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261021042350.907-1-hdanton@sina.com> X-Rspamd-Queue-Id: 9E08D40002 X-Stat-Signature: kz75sx9q5kiycgb8sc8ut5sg9spgorff X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792558582-738203 X-HE-Meta: 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 pUDn6EGf PcOtAy+bzbDQMc/6EwsCeMf66S7zO0HKpIN4PeWrZKnuI2vNwUbHqY8rm+U0M/mfDI/hryL7Wuk6N1rcdf5oSCSd/ETZHIBcEKC7AJ0FpNGyXNvI7P0DIgpm6pw0vSPYP9eF0Ir/Gf8ZvFiKVUkCTwUcVbwihP+/IenplVTkbUkrCXvbTpWNWB6jWS/wXxepmzZbPBBVOfSXkRnPDIGKkjvbqLWRIn+qABa1QIaz/QR2jyqmjI3B1a4I9NObHDtfTdMZKhJdxMKfrA17/oZBFBNu439jruLm9x2HPWo7WCZM0C6pZDYJSmqnB6dswgfch7inrsMiryG1lqN20mMmnkNLnrW3Lu16kfng6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On (26/10/21 12:23), Hillf Danton wrote: > On Wed, 21 Oct 2026 11:42:19 +0900 Sergey Senozhatsky wrote: > > Split struct zcomp_strm into separate compression (Write zcomp_cstrm) > > and decompression (Read zcomp_dstrm) streams, and split zcomp_ops > > context creation/destruction into create_cctx/destroy_cctx and > > optional create_dctx/destroy_dctx callbacks. > > > > This decouples Read (decompression) and Write (compression) paths so > > they no longer contend on the same per-CPU stream mutex (Writer vs > > Reader priority inversion). Currently, a (low priority) Writer that > > holds the stream mutex can be preempted by a (higher priority) Reader > > on the same CPU, which then blocks on that mutex until the Writer gets > > to run again and releases it, which can take a long time when there > > are other runnable tasks on that CPU. > > > Given lock like mutex, priority inversion happens from Monday to Friday, > but I wonder if you are inventing some wheels in 2026 if proxy excution > works for you. Reader-Writer split is a foundation for further improvements (like singleton recompression stream and so on).