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From: Yosry Ahmed To: Sergey Senozhatsky Cc: 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: 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-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0DCD81C000D X-Rspam-User: X-Stat-Signature: 3npjkzuub8zei4jpf97bujgtihgkmatn X-HE-Tag: 1768251419-490257 X-HE-Meta: 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 xL+bSucA YMBDjHg1FGDiIgLo/6vmtZ7Rrzt101D0QGN16iF5D3KT1xMjpE0kk3zhLOSr99yBXMqU7TWrsWK1iiHCFeH8TKmdVtHNMRcEXgywmG4+T2qA8UXffzKyOA5L8PUBPU+K9g+Zkm02NNkhuNJi45KNTP9311oyRQ672VV1PhOsHiNJ8XF4UDlgjaEEajcxOnBSfHEVlj1KkdFwSDyM= 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 Mon, Jan 12, 2026 at 02:07:24PM +0900, Sergey Senozhatsky wrote: > On (26/01/12 13:01), Herbert Xu wrote: > > On Fri, Jan 09, 2026 at 04:02:51PM +0000, Yosry Ahmed wrote: > > > > > > Herbert, do you mind taking a look at this? It looks sane to me except > > > for one question below. > > > > 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?