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b=HSSOZjVbACaTHAh1yK4L/NRqT1Na3DhszOVcUjsGdS1txy2IfGGyWfcEH4aup3OrZ aHSpCZmwug1e/IqhatX+a4f160We6zSXtvAij3J1eSSI4viMlBpuODrp01fQY/JHp9 0ea7VaLV+X+SXsEf9GwKpAu6UQDLi9TZe2zgfaGA= Date: Mon, 27 Apr 2026 11:22:25 -0700 From: Andrew Morton To: kasong@tencent.com Cc: Kairui Song via B4 Relay , linux-mm@kvack.org, Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Shakeel Butt , Lorenzo Stoakes , Barry Song , David Stevens , Chen Ridong , Leno Hou , Yafang Shao , Yu Zhao , Zicheng Wang , Baolin Wang , Kalesh Singh , Suren Baghdasaryan , Chris Li , Vernon Yang , linux-kernel@vger.kernel.org, Kairui Song , Qi Zheng Subject: Re: [PATCH v7 00/15] mm/mglru: improve reclaim loop and dirty folio handling Message-Id: <20260427112225.3f752a385f58bd7dfddfaa25@linux-foundation.org> In-Reply-To: <20260428-mglru-reclaim-v7-0-02fabb92dc43@tencent.com> References: <20260428-mglru-reclaim-v7-0-02fabb92dc43@tencent.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 7501EA000B X-Rspamd-Server: rspam04 X-Stat-Signature: 9xt7jgmb6tg3acy9ogxc1ycdqrknt3ug X-HE-Tag: 1777314154-55424 X-HE-Meta: U2FsdGVkX1/0j6z58DGJoIeefGDpT2QOEAP0luThfPVA0aqikAfMxFnMQfM888B2RxgzIPgY9+sSy2FChlRKpfM4fE8U61h9pZFZfSzII1/dkAW3M2VR1shTeC8nbpmZ7Xilu/pfamSmyb0mfpPNKoDfCDoj2Xp+uGBjBF5Tm9XUKS4/5OMui7Db9VTysA+mRj2wz/s/Wgic3YNYOeKIi37MjPjV1GbaoEEeu0ZYo489GhrmyY1yE3gfFgTaHUXR9TS9UhQZn7ZsgA1b/gMvac0udP7F/cb0EiA/AIk/14dZ5QRT+jtSEyIWivYYI2rvx+5W1zhpZbf+iYZ0mg7jNoL1AXPHy1yhPde5K/vmhxizJDL+ncvs7Eid9aPtSLmlqfsrH0SB7sOzSBcCpH8fU7RSyDlULACvvYs8nnrCf/sMTOqOU0TJGG5bHe7Vw7qdSvq87vM86ees2rmLS96Fec6kZDdieWzlG94fRdlkqTQJmUliodvD0lXqlDpeKmeC83u5Q5vomB46FpTAOjewSRPJMMQWxdIB6L7xmxiL4sAPrd2evmQLVGcnB+q6q5AqqXdUCVm7c7/wcippnaWobWOzC8I1ZWDvWaSfGQnMv837SLO4ZK/CL3K5mByWmI5pEdSqu65ga3FTas/bvpjhqK9iX9K+QMay6JFNhlN/jjdT3Oa1myETMB+T8CtfRjMTegmlzP1Y/ZiCx118+QPwj1TAS3ar1zUAtDxEXZ4m8963JtXjjZJpCUeqXcy5sZX7GRK99xThPep/w3J+qTZh2ZZaveXyw18xgRkuLDsSaEuF4jaGDEXvkN6Ycw32zKwXZGFBkIlV/wu+SXGeVZP0JXi571ma5AbqrtAUR35avR7YbaT6h9yA3JV6qyaY7OA/zXyob0tiIsArGdOGuqHxs4lQUkXUcD5v9HUXAjKCpNkndIpJ2LvUO4aN0rtxkyDlCRgbfOJYgXHeUW86yTs LPUgelmz bDVuJ2Cotnfa8RP8JIuIjtEZJyP//6b7NWtRPnI22+x/tFB6UzyNDBhjNTrvI+Q18uVlY4bLkStDhbgVdv1sFObd8PU0irlQY7ZWOak2d4xHjPTFboH5PA4McBlf/Y7+q78UDFCzRUoyNgP7qTPOJmHJGmEcb2F5j2fR9mYhs1qCHvhBAphkw2C0WDKmhEoKTWqBCZjPJDwohtpBeu5VtBHEdzGPO/BTMddTnkyxdQ/dl0l/gQjkvdBv6Lk2zxKmoA/0gssx5eG5v67p57H60+GqCWj2x3BUxBFZ38Qm19qx+aEaKz116weboguyyCYCmhgJSa0luc9huB8u4cXyPQ0n4hzgytlH6fS1xEduzNA0JhiyfRATmGXAZK5iEvdd8cQ3a6BraRaO5ELIN2lArDRhF27SWwX9Qz7RK5LOe8/ptcj1xcW1AVdtV10X3BXcoKb8Q9Vp46Rml0Wo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 28 Apr 2026 02:06:51 +0800 Kairui Song via B4 Relay wrote: > From: Kairui Song > > This series cleans up and slightly improves MGLRU's reclaim loop and > dirty writeback handling. As a result, we can see an up to ~30% increase > in some workloads like MongoDB with YCSB and a huge decrease in file > refault, no swap involved. Other common benchmarks have no regression, > and LOC is reduced, with less unexpected OOM, too. Thanks, I've updated mm.git's mm-new branch to this version. > Changes in v7: > - Fix swappiness not being effective with a standalone fix patch > from Barry Song. It's OK to be a standalone fix since that is not a > major bug but an unexpected behavior change, and shouldn't effect any > bisecting. I slightly adjusted the commit message as the subjcect is too > long and getting truncated for mail: > https://lore.kernel.org/linux-mm/20260425205759.1701-1-baohua@kernel.org/ > - Remove the min limit for calculating nr_to_scan: > https://lore.kernel.org/linux-mm/aet1hd9DfRH4aSOO@KASONG-MC4/ > Instead just revert to V1: > https://sashiko.dev/#/message/20260318-mglru-reclaim-v1-3-2c46f9eb0508%40tencent.com > Everyone was fine with that, the min limit in later version was > introduced to cover sashiko's review on V1, but now think again, that's > actually not a bug and instead could be beneficial. This min > check doesn't always make sense and there isn't any practical issue observed. > - Retest still looking very good in every case. Here's how v7 altered mm.git. (Looks small - did I mess this up?) --- a/mm/vmscan.c~b +++ a/mm/vmscan.c @@ -4788,8 +4788,13 @@ static int isolate_folios(unsigned long *isolate_scanned = scanned; break; } - - type = !type; + /* + * If scanned > 0 and isolated == 0, avoid falling back to the + * other type, as this type remains sufficient. Falling back + * too readily can disrupt the positive_ctrl_err() bias. + */ + if (!scanned) + type = !type; } return total_scanned; @@ -4909,18 +4914,14 @@ static long get_nr_to_scan(struct lruvec unsigned long nr_to_scan, evictable; evictable = lruvec_evictable_size(lruvec, swappiness); - nr_to_scan = evictable; /* try to scrape all its memory if this memcg was deleted */ if (!mem_cgroup_online(memcg)) - return nr_to_scan; + return evictable; - nr_to_scan = apply_proportional_protection(memcg, sc, nr_to_scan); + nr_to_scan = apply_proportional_protection(memcg, sc, evictable); nr_to_scan >>= sc->priority; - if (!nr_to_scan && sc->priority < DEF_PRIORITY) - nr_to_scan = min(evictable, SWAP_CLUSTER_MAX); - return nr_to_scan; } _