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Mon, 12 Jan 2026 18:36:55 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:3c61:f146:e418:e233]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-81f4433488esm6978569b3a.2.2026.01.12.18.36.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jan 2026 18:36:54 -0800 (PST) Date: Tue, 13 Jan 2026 11:36:47 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Sergey Senozhatsky , Herbert Xu , Andrew Morton , Nhat Pham , Minchan Kim , Johannes Weiner , Brian Geffon , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 2/2] zsmalloc: chain-length configuration should consider other metrics Message-ID: <5n73klpww36wzux64rmfa6iialqkrgw2ft34vtarwkzdq65yct@txn2ylzkfmr3> References: <9b7d6e6292c64f21b8d09def1b6723f02faffe88@linux.dev> <53zplsrqc66z4ea64cosy53zvttuuhgxr2ik7uw6i2zgluegyz@d3ulgntwnyw4> <2iophcy2e6vk72ypxeshmen66e7jhr52zr34parn4uw6vdyjef@frnpfrltrky2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: CB1E8C000D X-Stat-Signature: yg5ecewcmepfx5z9oo8rnzn5154efcbp X-Rspam-User: X-HE-Tag: 1768271816-485238 X-HE-Meta: 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 3TB7NHCw NA3451t4bumIu9ELFpc54180hQYAJdk9uap1DndQ7OZkV3pd6sXC6hCxrwtskEIE9XWX98iuUHIbVZfv99WsOY/UVPoeM+q0LTXNAwOn4wsLeqak4k7b36M2ZYr5LsZx+OVTlt7RAPi+xgAFK1R0Hua7rKj7b8H1pVIHiNyoBzRQfD74pld9DkIH0knMv8oWs0TxQsyOd9GhrN6L0fkL+hHmxSy/c7/y4dJph2qUQVO5aCmTmSHjC/A39gGQIKs27wzMDfTulm8DAkr7i6wZagG9XURs0sf/JFA1TN/5wKnWQ1jzTkfjcGr2LtDwKQlNGh7s1AxePvpe020+J3YXSFTM6wy5RLz3C00AlsSa2rKz7YOo= 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 (26/01/12 20:56), Yosry Ahmed wrote: > > > Looks alright to me too. > > > > > > > > + size_t sizes[2]; > > > > > + > > > > > + /* this object spans two pages */ > > > > > + sizes[0] = PAGE_SIZE - off; > > > > > + sizes[1] = mem_len - sizes[0]; > > > > > + > > > > > + sg_init_table(sg, 2); > > > > > + sg_set_page(sg, zpdesc_page(zpdesc), sizes[0], off); > > > > > + > > > > > + zpdesc = get_next_zpdesc(zpdesc); > > > > > + sg = sg_next(sg); > > > > > > > > Is this stateful? Will the SG list be returned pointing at the second > > > > page now? > > > > > > It makes no difference because we just called sg_init_table(sg, 2), > > > so sg_next(sg) is equivalent to &sg[1]. > > > > I did it this way for (sort of) consistency: sg next follows zpdesc next. > > Makes sense, I think I confused myself earlier. Do you plan to switch > the existing interfaces to use SG lists for both zswap and zram? Or does > zram still need the old interfaces? That's a good question. I don't know. I was thinking of providing SG-list based API for zswap first and keeping zram as is, for now. zram doesn't use crypto API at the moment so supporting new interface will come with extra work.