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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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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.