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Wed, 21 Oct 2026 19:06:58 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:5145:5add:2df6:4671]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1903d3ae06fsm10318111c88.19.2026.10.21.19.06.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 19:06:57 -0700 (PDT) Date: Thu, 22 Oct 2026 11:06:53 +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: <20261021075322.923-1-hdanton@sina.com> <20261022000822.938-1-hdanton@sina.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261022000822.938-1-hdanton@sina.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BC529140002 X-Stat-Signature: 5rddxsszcmh6ges957bbj4my6d5mqwnb X-Rspam-User: X-Spam-Status: No, score=-5.8 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-HE-Tag: 1792634819-230015 X-HE-Meta: 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 NNGjCgPA KOXmc+l7kEzSdv4cA7AUrJ5uqgJGtKGneKpvw9Qe9sg+eZo66Mn+UnHYfLrtyguF5pYJjJRNbn3ixswPrQNmoX7j0uuCeZazYf61y6XRCmGHcSc+ZmVVHTiYUYT4AR/h7EayGdd8+4M9ZPYjF0EMqoYm29eUj6OmBhFoLfalMC+nzh4T5RfVKQINJ0dT01vjtrBLx9bZaGqdHXKVEM+hg3Id6ulNKh5jf++VPy3fI5fnLmK8vIYqE6t3PZg+ChjSZGHvjOnun416e+C5jy07V4WbszDk72tEclJ07QZM7OnYFrqJdz3ueFhoELW8rILF3hIuqedppVATzOrEcAhdb/yq6LrDxJLrg7cjC 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 (26/10/22 08:08), Hillf Danton wrote: [..] > >>> 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). > >> > > But that split is not needed at all if PE works, yes? > > > > When the number of locks and tasks grows, I have increasing difficulty even > describing the lock chain that you in combination with Brian are unable to > handle. That is why in general PE is prefered over whatever wheels you can create. Hillf, if we reinvent the wheel then I'm very happy with this reinvention. But we don't. There is not a single reason for compression and decompression to be in the same context - they don't share a single byte. And there is no reason whatsoever to serialize them against each other. Compression and decompression should have been separate contexts from the beginning. While serializing decompression with a PE/PI-enabled mutex is cool, not having decompression serialization at all is way cooler. In addition, decoupling compression and decompression leads to a much saner recompression stream design, which saves considerable amount of per-CPU memory. That's what this patch does for us. The commit message probably can be better, but other than that I'm happy with this series.