From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18A8D3A1E7F for ; Wed, 8 Apr 2026 08:27:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775636879; cv=none; b=AlQYdcSEfYreXIuUv50NByOlq75SwMAQimYDmOvllYiySJwZhBjtmn2iloJFZyfyQVfyohcmjNMg9E2BkvkgMLFBnls7dhlD0Q09gkASoxrmckl+EDR6zYinlDty+QwdN9T6ekMIyq3ShrBydyGyeWMJW4e4ikYMukZS8p6Uh0g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775636879; c=relaxed/simple; bh=FXDM1t5LoqjEwZAVL11OxykELtycP5IulEyoCy0yCIk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NcnFRp/+o8CKqFfCLAFSe3wzE7v42iINgyqOo58mzurPJyt2yOVY9gUd4Hf7sas3p4KTOWmvl9wUHVh8ML4Obz0BYoEaHtEzWiGlNpmCf0LB20OIAY3R8xvoqGBuHBDoIkIks70w4Ol9peIDQfu4d7r+qPeN2i09hk/VyJuuIPI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.177]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4frGQ94kYmzYQtr3 for ; Wed, 8 Apr 2026 16:27:13 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 7BF1540539 for ; Wed, 8 Apr 2026 16:27:47 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP1 (Coremail) with SMTP id cCh0CgBHS9uBEdZpZ4E8Dw--.57995S2; Wed, 08 Apr 2026 16:27:47 +0800 (CST) Message-ID: Date: Wed, 8 Apr 2026 16:27:45 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 05/14] mm/mglru: scan and count the exact number of folios To: kasong@tencent.com, linux-mm@kvack.org Cc: Andrew Morton , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Barry Song , David Stevens , Leno Hou , Yafang Shao , Yu Zhao , Zicheng Wang , Kalesh Singh , Suren Baghdasaryan , Chris Li , Vernon Yang , linux-kernel@vger.kernel.org, Qi Zheng , Baolin Wang References: <20260407-mglru-reclaim-v4-0-98cf3dc69519@tencent.com> <20260407-mglru-reclaim-v4-5-98cf3dc69519@tencent.com> Content-Language: en-US From: Chen Ridong In-Reply-To: <20260407-mglru-reclaim-v4-5-98cf3dc69519@tencent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:cCh0CgBHS9uBEdZpZ4E8Dw--.57995S2 X-Coremail-Antispam: 1UD129KBjvJXoW3JFyxAr4Dur4rtr43Kw4Uurg_yoW3GF4Upa 9xG342yFW8Jr43KrWvqr4rCr43CrWfJ34DAry3Aw1SkFn3XFy8Ka13Gw1UtrWUuryDCFWF v3W7KrZ7u3WjqrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv0b4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r4a6rW5MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVW8ZVWr XwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU0 s2-5UUUUU== X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ On 2026/4/7 19:57, Kairui Song via B4 Relay wrote: > From: Kairui Song > > Make the scan helpers return the exact number of folios being scanned > or isolated. Since the reclaim loop now has a natural scan budget that > controls the scan progress, returning the scan number and consume the > budget should make the scan more accurate and easier to follow. > > The number of scanned folios for each iteration is always positive and > larger than 0, unless the reclaim must stop for a forced aging, so > there is no more need for any special handling when there is no > progress made: > > - `return isolated || !remaining ? scanned : 0` in scan_folios: both > the function and the call now just return the exact scan count, > combined with the scan budget introduced in the previous commit to > avoid livelock or under scan. > > - `scanned += try_to_inc_min_seq` in evict_folios: adding a bool as a > scan count was kind of confusing and no longer needed to, as scan > number should never be zero as long as there are still evictable > gens. We may encounter a empty old gen that return 0 scan count, > to avoid that, do a try_to_inc_min_seq before isolation which > have slight to none overhead in most cases. > > - `evictable_min_seq + MIN_NR_GENS > max_seq` guard in evict_folios: > the per-type get_nr_gens == MIN_NR_GENS check in scan_folios > naturally returns 0 when only two gens remain and breaks the loop. > > Also change try_to_inc_min_seq to return void, as its return value is > no longer used by any caller. Move the call before isolate_folios so > that any empty gens created by external folio freeing are flushed, and > add another call after isolate_folios to also flush empty gens that > isolation itself may create. > > The scan still stops if there are only two gens left as the scan number > will be zero, this behavior is same as before. This force gen protection > may get removed or softened later to improve the reclaim a bit more. > > Reviewed-by: Axel Rasmussen > Signed-off-by: Kairui Song > --- > mm/vmscan.c | 60 ++++++++++++++++++++++++++++++------------------------------ > 1 file changed, 30 insertions(+), 30 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 462ca0fa2ba3..d3fd5bb56cce 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3878,10 +3878,9 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness) > return true; > } > > -static bool try_to_inc_min_seq(struct lruvec *lruvec, int swappiness) > +static void try_to_inc_min_seq(struct lruvec *lruvec, int swappiness) > { > int gen, type, zone; > - bool success = false; > bool seq_inc_flag = false; > struct lru_gen_folio *lrugen = &lruvec->lrugen; > DEFINE_MIN_SEQ(lruvec); > @@ -3907,11 +3906,10 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, int swappiness) > > /* > * If min_seq[type] of both anonymous and file is not increased, > - * we can directly return false to avoid unnecessary checking > - * overhead later. > + * return here to avoid unnecessary checking overhead later. > */ > if (!seq_inc_flag) > - return success; > + return; > > /* see the comment on lru_gen_folio */ > if (swappiness && swappiness <= MAX_SWAPPINESS) { > @@ -3929,10 +3927,7 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, int swappiness) > > reset_ctrl_pos(lruvec, type, true); > WRITE_ONCE(lrugen->min_seq[type], min_seq[type]); > - success = true; > } > - > - return success; > } > > static bool inc_max_seq(struct lruvec *lruvec, unsigned long seq, int swappiness) > @@ -4686,7 +4681,7 @@ static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct sca > > static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > struct scan_control *sc, int type, int tier, > - struct list_head *list) > + struct list_head *list, int *isolatedp) > { > int i; > int gen; > @@ -4756,11 +4751,9 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); > if (type == LRU_GEN_FILE) > sc->nr.file_taken += isolated; > - /* > - * There might not be eligible folios due to reclaim_idx. Check the > - * remaining to prevent livelock if it's not making progress. > - */ > - return isolated || !remaining ? scanned : 0; > + > + *isolatedp = isolated; > + return scanned; > } > > static int get_tier_idx(struct lruvec *lruvec, int type) > @@ -4804,33 +4797,36 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness) > > static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > struct scan_control *sc, int swappiness, > - int *type_scanned, struct list_head *list) > + struct list_head *list, int *isolated, > + int *isolate_type, int *isolate_scanned) Nit: too many parameters for this function. > { > int i; > + int scanned = 0; > int type = get_type_to_scan(lruvec, swappiness); > > for_each_evictable_type(i, swappiness) { > - int scanned; > + int type_scan; > int tier = get_tier_idx(lruvec, type); > > - *type_scanned = type; > + type_scan = scan_folios(nr_to_scan, lruvec, sc, > + type, tier, list, isolated); > > - scanned = scan_folios(nr_to_scan, lruvec, sc, type, tier, list); > - if (scanned) > - return scanned; > + scanned += type_scan; > + if (*isolated) { > + *isolate_type = type; > + *isolate_scanned = type_scan; > + break; > + } > > type = !type; > } > > - return 0; > + return scanned; > } > > static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > struct scan_control *sc, int swappiness) > { > - int type; > - int scanned; > - int reclaimed; > LIST_HEAD(list); > LIST_HEAD(clean); > struct folio *folio; > @@ -4838,19 +4834,23 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > enum node_stat_item item; > struct reclaim_stat stat; > struct lru_gen_mm_walk *walk; > + int scanned, reclaimed; > + int isolated = 0, type, type_scanned; > bool skip_retry = false; > - struct lru_gen_folio *lrugen = &lruvec->lrugen; > struct mem_cgroup *memcg = lruvec_memcg(lruvec); > struct pglist_data *pgdat = lruvec_pgdat(lruvec); > > lruvec_lock_irq(lruvec); > > - scanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness, &type, &list); > + /* In case folio deletion left empty old gens, flush them */ > + try_to_inc_min_seq(lruvec, swappiness); > > - scanned += try_to_inc_min_seq(lruvec, swappiness); > + scanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness, > + &list, &isolated, &type, &type_scanned); > > - if (evictable_min_seq(lrugen->min_seq, swappiness) + MIN_NR_GENS > lrugen->max_seq) > - scanned = 0; > + /* Isolation might create empty gen, flush them */ > + if (scanned) > + try_to_inc_min_seq(lruvec, swappiness); > > lruvec_unlock_irq(lruvec); > > @@ -4861,7 +4861,7 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > sc->nr.unqueued_dirty += stat.nr_unqueued_dirty; > sc->nr_reclaimed += reclaimed; > trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, > - scanned, reclaimed, &stat, sc->priority, > + type_scanned, reclaimed, &stat, sc->priority, > type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); > > list_for_each_entry_safe_reverse(folio, next, &list, lru) { > This patch makes the code easier to follow. Looks good to me. Reviewed-by: Chen Ridong -- Best regards, Ridong