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Thu, 07 Dec 2023 10:24:19 -0800 (PST) MIME-Version: 1.0 References: <7df7e478-bd93-03df-5b10-19308f416e95@quicinc.com> In-Reply-To: <7df7e478-bd93-03df-5b10-19308f416e95@quicinc.com> From: Yu Zhao Date: Thu, 7 Dec 2023 11:23:41 -0700 Message-ID: Subject: Re: high kswapd CPU usage with symmetrical swap in/out pattern with multi-gen LRU To: Charan Teja Kalla Cc: Jaroslav Pulchart , Daniel Secik , Igor Raits , Kalesh Singh , akpm@linux-foundation.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0B5F340025 X-Stat-Signature: 18nkguc53wjb95a6pxx83eeaowanakye X-Rspam-User: X-HE-Tag: 1701973460-286824 X-HE-Meta: U2FsdGVkX19yF/Z91X2o1G6+DvLFcQb+RiY6Ewc08ou+wiXKATqSeDyQIZp0qg27XH2VfDT2gyivY0ev/6vBinEeihxobmCIDHfAVMn+Rwc3cb7xm8Fq3sLFr3hL7zw7WPjL99qS8NgiWyeTPmCCo8iCZmJLYUTFaxwAtPNH7p7sW7kY1RVAql2O1LhpYDR8OkbXuD4+X4Pwkp2ywkRco+Z56yo9U/rYAnyzUIxc2Bz4ny7CKcdLDvUt98kVFMUk8t/n19m3xrQ/sWBUcdyFzdpx6bAKs4b4HkD9lQwBvYRpkZxihhdjmJ+qPwIkTrNLAB0ziWgx35rFNKvZm2AE3rNLRJUS8JJcNuEnEJulKa6blFMzOOWws1wq3ehwzdDb3EV8nSREsuC2NEcR+i++WRH0mVIUt2TckljYbEkHU2to1VnIg012d+0Sl7PQ23OKR8IGRYGFJCHiQ1IJOTB86BrIomoeZpdJ+zGtng+TZIrkLFAS4LJElF6in1LV6nJ+qJHlnpc1a/+KMfsErDZqDg/Lz68YZVtXXc00JX/T9e3sZDq89qUjkR/aaoM0sdZMeY8A0xbaIkbRUK2wlUjk7wg4qQ/ZTfcEPBcshUfbEeqbtE/zobG2usuNnbXVOmuha2MT8EkdIG/fC2+2PQih0/HjX8AjIBRC1XG0fZe3noTU+nfJX5tkCicuxxCXGqiMQWVa1b6IcUQvJ1AFkh+aPtfqbbF1vXqsFgri/YkvimgnW7gRbUOltEOZG+zh5ZHFPUH31ZCiobgol+gXOFShsQOkbrgQ+qeYAneHqsCKarvgGYO5iHgUwrm/XLKdp9Yq8VpNzF+tcm5OQs4rG2+2t1uc0cO0ZGVz7jiAH6bFegUcJQGEVoW9ihY/aQJcQ+edXESB+jtKzmEfkrzJooFq8HQQRgDkGIgOH2alg66JXKoGkRVJq6ft5lNJNIeU64StyYrZJFcnYZGu9W9GTKH wDW5J4Fv Z5vd0vDViP7ZrkFMC5SuKBBUHuAaSGNrdB/NDz6F96YFY+7uAxfftR+N5KuE04u1qPNgsyBhBbaxOZxEsL2bpzOrKwUAEnJsPKOI3BsIqOxlZyZ/rTHV6vcsCD1eBaLGsBgcYDj9UJpF5SRCgKo6Tyc6h1FHcJrVqBxtU5Xn0xDbe257uGjxqQqygB/suy0PB79J/+3IHO+np/U1Mw/EfTC+UULO9OzDe20Tz/2d8p6AGsQIn850GovmPuQ+BHF0qb2jMbT0psSqsLsapn+z1ZStX4c+qtLVjbjP+ZRzPULErUEBKcNu0SD+gZw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000089, 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, Dec 7, 2023 at 1:47=E2=80=AFAM Charan Teja Kalla wrote: > > Hi yu, > > On 12/2/2023 5:22 AM, Yu Zhao wrote: > > Charan, does the fix previously attached seem acceptable to you? Any > > additional feedback? Thanks. > > First, thanks for taking this patch to upstream. > > A comment in code snippet is checking just 'high wmark' pages might > succeed here but can fail in the immediate kswapd sleep, see > prepare_kswapd_sleep(). This can show up into the increased > KSWAPD_HIGH_WMARK_HIT_QUICKLY, thus unnecessary kswapd run time. > @Jaroslav: Have you observed something like above? > > So, in downstream, we have something like for zone_watermark_ok(): > unsigned long size =3D wmark_pages(zone, mark) + MIN_LRU_BATCH << 2; > > Hard to convince of this 'MIN_LRU_BATCH << 2' empirical value, may be we > should atleast use the 'MIN_LRU_BATCH' with the mentioned reasoning, is > what all I can say for this patch. Yeah, we can add MIN_LRU_BATCH on top of the high watermark.