From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) (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 48E483D2FEC for ; Tue, 31 Mar 2026 08:04:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774944279; cv=none; b=eS6Fs0xeR3mpgOpoXpBRL748Ylo/13vn2VGgQM+IECnJYuIcv0wQwwRQKQnK0JB1lAeWFTe0ahRr5043vKTZUoKsFS8vg3iunci6r6GelKCArqhh/4FW3itl7bM7w70I1FATXkR+Kw2G0yOfBenh80/m+fVnzRI62LhE0Impjxw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774944279; c=relaxed/simple; bh=hJdLbN9QLn0wl3KJrfIy7c70WxQyj19tnIkTw5P32b8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HSE2dp7DJiEHEtjHrmIQv6u42Ldkl7xPUm2QMc7gR4SMNuAMvcOLwNj4BTDjX3pP1AsWZqwGjXi9aDByILPnV+hqA56rduGb4fW8Jc6ZyuB+cuzoriKGpVMmImvqzl9GIxJIbJk2DgitD8eoh6WyhGPkBLKBpoGOX9CbVDe9ysg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=TBzFwW+A; arc=none smtp.client-ip=115.124.30.118 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="TBzFwW+A" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1774944274; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=aTnq0mmzjppffXpYB5B4b2z/irJ0T8mlES9cozy6Bi0=; b=TBzFwW+Ac1heczy/wE+Dn8LXwGlHEzXECm00R/+86yQGUW0FiLXFsQrHDAxbodqHZVMI6Iy8DNBwudGdld6ehxf6hkKul+ka1MQrT+xxj/dh7wjDktWdhb0nw5C8gyjtkfVbgHLfXVH61PwJOr/ef9iqblUYeVpKb+VrJtdpQO4= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R931e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037033178;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=25;SR=0;TI=SMTPD_---0X03ffKP_1774944271; Received: from 30.74.144.129(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X03ffKP_1774944271 cluster:ay36) by smtp.aliyun-inc.com; Tue, 31 Mar 2026 16:04:32 +0800 Message-ID: <3ef1cb78-5110-4326-bde1-d929f638b8f6@linux.alibaba.com> Date: Tue, 31 Mar 2026 16:04:30 +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 v2 05/12] 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 , Chen Ridong , Leno Hou , Yafang Shao , Yu Zhao , Zicheng Wang , Kalesh Singh , Suren Baghdasaryan , Chris Li , Vernon Yang , linux-kernel@vger.kernel.org, Qi Zheng References: <20260329-mglru-reclaim-v2-0-b53a3678513c@tencent.com> <20260329-mglru-reclaim-v2-5-b53a3678513c@tencent.com> From: Baolin Wang In-Reply-To: <20260329-mglru-reclaim-v2-5-b53a3678513c@tencent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/29/26 3:52 AM, 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 directly 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. Make sense to me. > > - `scanned += try_to_inc_min_seq` in evict_folios: adding a bool as a > scan count was kind of confusing and no longer needed too, as scan > number will never be zero even if none of the folio in oldest > generation is isolated. Yes, agree. > > - `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 move try_to_inc_min_seq before isolate_folios, so that any empty > gens created by external folio freeing are also skipped. This part is somewhat confusing. You probably mean the case where the list of that gen becomes empty via isolate_folio(), right? If that's the case, the original logic would remove the empty gens produced by isolate_folio() after calling try_to_inc_min_seq(). However, with your changes, this removal won't happen until the next eviction. Does this provide any additional benefits? Or could you describe how this change impacts your testing? > 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. > > Signed-off-by: Kairui Song > --- > mm/vmscan.c | 46 +++++++++++++++++++++++----------------------- > 1 file changed, 23 insertions(+), 23 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ab81ffdb241a..c5361efa6776 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4686,7 +4686,7 @@ 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 +4756,9 @@ 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 +4802,36 @@ 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) > { 8 parameters:), can we reduce some of them? > 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 +4839,18 @@ 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); > - > - scanned += try_to_inc_min_seq(lruvec, swappiness); > + try_to_inc_min_seq(lruvec, swappiness); > > - if (evictable_min_seq(lrugen->min_seq, swappiness) + MIN_NR_GENS > lrugen->max_seq) > - scanned = 0; > + scanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness, > + &list, &isolated, &type, &type_scanned); > > 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) { >