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Received: from loth.rohan.me.apana.org.au ([192.168.167.2]) by formenos.hmeau.com with smtp (Exim 4.96 #2 (Debian)) id 1vdl18-00F386-0p; Thu, 08 Jan 2026 16:05:15 +0800 Received: by loth.rohan.me.apana.org.au (sSMTP sendmail emulation); Thu, 08 Jan 2026 16:05:14 +0800 Date: Thu, 8 Jan 2026 16:05:14 +0800 From: Herbert Xu To: Yosry Ahmed Cc: Sergey Senozhatsky , 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: <5p4iyah6zlrnxpbsis32c4m5lrjj3pq7xwcugq35d2entwfai2@n2r6y3ga2ie5> <7q5gqpfshnc3lfhzxughpks3fc2knw2delpm5io2oe54monydl@5isuxnjputjr> <9b7d6e6292c64f21b8d09def1b6723f02faffe88@linux.dev> <53zplsrqc66z4ea64cosy53zvttuuhgxr2ik7uw6i2zgluegyz@d3ulgntwnyw4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0C451140010 X-Stat-Signature: b5krhs4tfhgjd8rs8e7cddiez3e8mcsb X-Rspam-User: X-HE-Tag: 1767859544-623119 X-HE-Meta: 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 NqQzAMe+ S1vYxbhXY4emIiPVMVFd8QEe4FgoLKjTRdCKaMKsPEKi8/iYltEvIGqdSzSUYIDMMwDDnDfM6hpZfVemmjzgWm2R3nV/rIQ5NhuT+QKhhnZuM++y+yUFMUrU3/tjB/OHn0ra13wQBoeDqf4tRE3rg81Q4vvajJyNxyMtlsqAknaYs4lxpmuT0SRw+7TLUL7GdKH1errRse3okMnxMWG5WLzCs/bnHdVm3CuGlGFM2X+Mgs1SWGYc1mF4FXM3aeqC0RV7Y96IJW8nl8wL454upaCH/gRDkmUpRKa2V 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 Thu, Jan 08, 2026 at 08:01:20AM +0000, Yosry Ahmed wrote: > > IIUC based on Herbert's previous response, crypto and scomp already > support passing in a discontiguous SG-list. So for zswap, if zsmalloc > returns an SG-list, it will just be passed as-is to the crypto API. > > If zram can also use the SG-list, then we can completely drop the > memcpy() logic from zsmalloc. > > Herbert, please correct me if I am wrong. You're correct. The SG support has always been there. You can use that today and scomp will perform the memcpy for you if and only if it's necessary. The algorithm-specific SG support would simply be a performance enhancement that eliminates the memcpy entirely for whichever algorithm that we choose to implement it for. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt