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Tue, 10 Nov 2026 22:05:17 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:ad6a:b446:df00:78dc]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b17e313932sm2766371a91.16.2026.11.10.22.05.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 22:05:16 -0800 (PST) Date: Wed, 11 Nov 2026 15:05:11 +0900 From: Sergey Senozhatsky To: Nhat Pham Cc: Sergey Senozhatsky , Andrew Morton , Yosry Ahmed , Johannes Weiner , Brian Geffon , Minchan Kim , Richard Chang , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 10/11] zsmalloc: fold zs_obj_write() into zs_store() Message-ID: References: <20261110054836.1515030-1-senozhatsky@chromium.org> <20261110054836.1515030-11-senozhatsky@chromium.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DFED71C0004 X-Stat-Signature: 8qh8t5kg3gr76m6d39xr6pbtrau744pd X-Rspam-User: X-HE-Tag: 1794377118-754765 X-HE-Meta: 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 dbk99B9q e2R0eJFkFdweeQ6itmjlmCbCkudAK6hiw3RJVO+kBvF1b13zYgmWgRUYc+sCIkAJ9NBlcUrqc0FHj7sEjW0I1Fenu2ZmeMuu3RCZXJyMAlW7y0WJmpvHPw29SNXpZGm3/jPsjcNcSva3xkAnqi61RqyePqhDHbhiunRFH96jngJXT1Kr5LxjP1UH6gr9LGUSXOHV2PLc+qlacLaCUvFcMMZvcnUTGYOH1L524FPA1vaaGeMRTst/DjXU9VM2r2dtI5MEh3y+hVSmdfate4pL3cPfeBqZOy3iZPNkw+lozLxNWIA4vZxQhIJBNTxSDn4AQ5q8AjUvSOGj6nzAu8NgH3ozRNv3UGZSikATqcovyrOJkcz7MavVQDgUu6Y9Um/1V/WF3P9KDgmOsTHI5B4ys5XCFGFrGektT6KyT 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 (26/11/10 11:01), Nhat Pham wrote: > On Mon, Nov 9, 2026 at 10:49 PM Sergey Senozhatsky > wrote: > > > > zram and zswap always call zs_obj_write() right after zs_malloc(), and > > zs_obj_write() has to take pool->lock and look up object location > > again, which zs_malloc() just did. > > > > Replace zs_malloc() and zs_obj_write() with one single zs_store() > > call. > > > > zs_store() takes zspage read lock under class->lock, before it drops > > class->lock to copy the data, while zs_obj_write() used to take it > > under pool->lock. Compaction and page migration already take zspage > > lock under class->lock, so this follows the existing pool->lock -> > > class->lock -> zspage->lock order. We don't need pool->lock there, > > zs_store() doesn't look up the object via the handle, it already has > > the zspage from the allocation. > > Oh nice, this looks like it'd save a pool lock acquisition? > > That (effectively global) lock can be quite contend-y under memory > fragmentation, etc... Right.