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Tue, 20 Jan 2026 19:49:52 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:a85f:a6d:c028:515a]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-81fa10cf1e6sm13284094b3a.26.2026.01.20.19.49.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jan 2026 19:49:52 -0800 (PST) Date: Wed, 21 Jan 2026 12:49:47 +0900 From: Sergey Senozhatsky To: Yosry Ahmed , Herbert Xu Cc: Andrew Morton , Johannes Weiner , Nhat Pham , Chengming Zhou , Sergey Senozhatsky , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: zswap: Use SG list decompression APIs from zsmalloc Message-ID: References: <20260121013615.2906368-1-yosry.ahmed@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260121013615.2906368-1-yosry.ahmed@linux.dev> X-Rspam-User: X-Rspamd-Queue-Id: C1C82180006 X-Stat-Signature: 3c9dw8yzxcuwh7bach4efzmsrcr9h4yf X-Rspamd-Server: rspam02 X-HE-Tag: 1768967393-455902 X-HE-Meta: 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 RdVYOq33 zQQauz2Vj1TJy2/87m0NRxCEbQyhinFbCXWFPDy78rj/vILJnm3WazsEZu3RornO58mdFGSwgzU/85HRBffUhzwB22kEXbmO0YTnRDbKse86FTTaqhwr7XArf2nuY3rQ5ZOzOOvV9xPYUpewnrWx8rzIWNNfHlhrZcQZhW8pAD+19VdRNDPZxbbw6KxVmXaZoX9mnKWwOFgpD+pfg1hHWt+7UoITo4YhtTicH2LVgOJeaGxsoTvi0Csd9DPPWNuA8Uev73XYjOfi6uJVjvi1uumPmRkIspfpqJWSxQsMN4+BeA0K9xgTdm84VLzm3x3bmihhKOD+Oic+DlzY8ELRG+gjZ98YOorWZR36Hu5By/CAVzis= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (26/01/21 01:36), Yosry Ahmed wrote: > Use the new zs_obj_read_sg_*() APIs in zswap_decompress(), instead of > zs_obj_read_*() APIs returning a linear address. The SG list is passed > directly to the crypto API, simplifying the logic and dropping the > workaround that copies highmem addresses to a buffer. The crypto API > should internally linearize the SG list if needed. > > This avoids the memcpy() in zsmalloc for objects spanning multiple > pages, although an equivalent operation will be done internally by > acomp/scomp. However, in the future compression algorithms could support > handling discontiguous SG lists, completely eliminating the copying for > spanning objects. LGTM. Once the API lands I think we'll be quite interested in discontiguous SG lists support in lzo-rle/lzo and lz4 (most commonly used primary S/W compressors in zram).