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Fri, 08 Dec 2023 00:03:53 -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: Jaroslav Pulchart Date: Fri, 8 Dec 2023 09:03:27 +0100 Message-ID: Subject: Re: high kswapd CPU usage with symmetrical swap in/out pattern with multi-gen LRU To: Charan Teja Kalla Cc: Yu Zhao , Daniel Secik , Igor Raits , Kalesh Singh , akpm@linux-foundation.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 49EA62000A X-Rspam-User: X-Stat-Signature: ngh3qwcso5zp4bac9bx4ugrszeuzneo4 X-Rspamd-Server: rspam03 X-HE-Tag: 1702022635-359648 X-HE-Meta: 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 OjLDRKWw 6u6d37TZ+102gnRqsYJVXRGMZa0V/UBSTRKlRFbu85IhVn5OKYcCRIAkN0HGFz+9vOy1pDL+FVwzQngfLedsIIDro3sPd/59+Jne/vIbRe5M5F6cIV57u3nHquV2pp4/5IfNIulGEn1bYyRCoKsXLp2uFgcu3VExOlb8fkM1Mf75+oZYEsKaeyPH0mSjKF778oYUhFUFJUb6tCRjfA8qz4tpLbidejP9RSVLP X-Bogosity: Ham, tests=bogofilter, spamicity=0.047738, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > 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? I do not see any unnecessary kswapd run time, on the contrary it is fixing the kswapd continuous run issue. > > So, in downstream, we have something like for zone_watermark_ok(): > unsigned long size = 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. > > + mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ? > + WMARK_PROMO : WMARK_HIGH; > + for (i = 0; i <= sc->reclaim_idx; i++) { > + struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i; > + unsigned long size = wmark_pages(zone, mark); > + > + if (managed_zone(zone) && > + !zone_watermark_ok(zone, sc->order, size, sc->reclaim_idx, 0)) > + return false; > + } > > > Thanks, > Charan -- Jaroslav Pulchart Sr. Principal SW Engineer GoodData