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Wed, 21 Oct 2026 12:24:02 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 8999416291657 X-SMAIL-UIID: F14EAB6385CA47FAA0CA6358ECCCDE05-20261021-122402-1 From: Hillf Danton To: Sergey Senozhatsky Cc: 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 Date: Wed, 21 Oct 2026 12:23:48 +0800 Message-ID: <20261021042350.907-1-hdanton@sina.com> In-Reply-To: <20261021024236.1787884-10-senozhatsky@chromium.org> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D79DC40007 X-Stat-Signature: p1xj8i8i38r55jk37gox7x99quy8x89s X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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: 1792556648-290544 X-HE-Meta: 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 AOvEoAi5 WrYrLOHhek+7ME+n+nLueHXVBc33Cgcy/V0i5C/XWT2/oMWfGB3mE87uvcg+8I96yqex1phjUSsGLHfP8FlYC/n0VNMAdGRu7OlRPCrsSdVYOValM0TBy8Pel5inmtQFMrSspVrJDuXL7LjziUp340WqHH9KjnFxflH3ziEDvlqwbPGyXYSWvWpYdr9yzg+ptSDUPDLViSAZT9/hENQ03LTHOv1XZHL3hLA6pvE9z4Nc05v4N2denYsEkvf3AMZ6ZCzSk8CRoD97tIw8wZcNnsa/jINW/c+AW0Ak3S9VTfyHuLuOpvP8LoYP+Nw== 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 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.