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Mon, 22 Jan 2024 11:49:42 -0800 (PST) MIME-Version: 1.0 References: <20240117-b4-zswap-lock-optimize-v2-0-b5cc55479090@bytedance.com> <20240117-b4-zswap-lock-optimize-v2-2-b5cc55479090@bytedance.com> In-Reply-To: <20240117-b4-zswap-lock-optimize-v2-2-b5cc55479090@bytedance.com> From: Yosry Ahmed Date: Mon, 22 Jan 2024 11:49:05 -0800 Message-ID: Subject: Re: [PATCH v2 2/2] mm/zswap: split zswap rb-tree To: Chengming Zhou Cc: Andrew Morton , Nhat Pham , Chris Li , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: AA3F9A0013 X-Stat-Signature: ybcui4puhbzkoxk5mkrbyoj46burxtsc X-Rspam-User: X-HE-Tag: 1705952984-5303 X-HE-Meta: U2FsdGVkX1/uRFNxMbKWY7WLazNb2+9iteGkDl/ChjXzDCPRaB8Y8tpllbrFSrlEAe7yryAap+SKgAAgCX9oGjxXqrY3XKOgfYU4z41gndkOb0gJQ7XpTloGdCSj+zqmqfQ7yZQTZMurRMqWsveU5T0KlJwwMCQjuUgPGfhiHkEao1uxHs8lOg+wbE4P0UYIyYUmwE2ZdobADBtbIReB+wlKqw4qiJ/aYOxTmZrhRYqtyXIM12uWZ6q2pBRTueuJUptZ618yFkcRadaK0l29sizxXKhvwC/qiycXWW2udkGntEY4etS3VNIUKRJv+mQiOQNkv9LVAzv8rktqvOjIG7mxx0TdMnOpUDDnrh2+MHup6YKPdNBoRDTLlxICYOKJTYEfZCTHTGDNurg1MTJL96WRIQ7HHwe9wggvfMT9Vdh8hWmnz0iI/OfYfycNktjZQRiec7qKAq1uMJ21N3BWzspyfhw9izHZ+o5in09oOGQ4HnNI/DazjgfyxsMOq/TXxbxzTSSbIi3EZpNF3BFrvYwGfiOQQQPRNq0tpD0TnbkEBztSm6EAimX5BQW1FbhSxHxh5asfR4naWJXmX5Je0fyLDzpOUhorCb7rg3Jr9zINxusQb9ZvEltQSGaECqlp2REupbWhCdNzuYWdK26+6xOK2huxOgb3gWi6D8PkDCBE+c0zDE7+aLkHfbVhP7Rsxs61XtPx73T09pv76KEtKCje2sQFPv9TwN4mzrJcyIYJ9DcuzhUA08CeACwj6lWwFYUxHFaLiu1i8Kj/ZANjwgYTJD9voApfTPDJV7ychp2h6EwATr/auUKnLPQSIOBtdXWG+Z/uYF67h8cg88zCHncIYam9CnDmyCFgDSIajHG8Vij6vR2qr7gRvs089BCTvsOQ7XpWB+5ZpV2JksbGixRKD2rvjih8vAG+Ca8fq0CJCiU3mzSc8HEsaLa0TsCKfD6ekRqGHWaycmNTCDi Ki9E4vQ4 08PADwQcQUsm1NIN8BDIm/Rn7eowQM97qUqUlj9bR6NZL5p2e1Nm1KD1odX/fNiaaTpgh00QBC6amlDeeHkTu0+gOvDv1pY8GLsIvrSKXgsnxr2eKb3hxVxJQ5wSigZirDimLTTEu53PDOg7W+WtK4jeGanXtq14oVdUC3DT8QWG0oPzl8okF8Krk8dAFmhUUVe6jcUHtFms2mFOBXEyE5z9kda11LIu2ac3HyxGfkvkj9rhJLPxLmLpnWixLwpfDLC0Tjy1u65AzpPyMJFmY9kw9ng5Qd7Y6m77IT2HkTRVbW+BIqtlEEvkITZ7wAF6lozQyxtqqV8vyxERxeOOY+v/SSH/aAK04rzVnBdqbTEXCUiNbWBjhVWxu5PU/OD2pr+XfBdBKSdMAV9o= 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 Fri, Jan 19, 2024 at 3:22=E2=80=AFAM Chengming Zhou wrote: > > Each swapfile has one rb-tree to search the mapping of swp_entry_t to > zswap_entry, that use a spinlock to protect, which can cause heavy lock > contention if multiple tasks zswap_store/load concurrently. > > Optimize the scalability problem by splitting the zswap rb-tree into > multiple rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M), > just like we did in the swap cache address_space splitting. > > Although this method can't solve the spinlock contention completely, it > can mitigate much of that contention. Below is the results of kernel buil= d > in tmpfs with zswap shrinker enabled: > > linux-next zswap-lock-optimize > real 1m9.181s 1m3.820s > user 17m44.036s 17m40.100s > sys 7m37.297s 4m54.622s > > So there are clearly improvements. If/when you respin this, can you mention that testing was done with a single swapfile? I assume the improvements will be less with multiple swapfiles as lock contention should be better. > > Acked-by: Johannes Weiner > Acked-by: Nhat Pham I think the diff in zswap_swapoff() should be much simpler with the tree(s) cleanup removed. Otherwise LGTM. Acked-by: Yosry Ahmed