From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-15.mta1.migadu.com [95.215.58.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AFA23448CF2 for ; Wed, 19 Aug 2026 10:16:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787134585; cv=none; b=rujHF+2edYXM2CJkUfQVpwplH6zS5RMmWNqbgORE3jdlKtVovMqUH2ho6/OqZjfW76Ta3JEg+kpl13bmfJgZo7lzF/O2BHhy673gaQbCHBTSG3wGTDQKyoPMRY/g58P6tEsA+kkTj5rwWdZ0+1LvtWXenLAnFV/tvtTHHU+P44c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787134585; c=relaxed/simple; bh=lrdTAluOUYWs62O0PpRF6nh/ALgtREIgbj5lfiADRdg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=H1aCVqPe0hA2baTq2mzjNfRqlMynmm4qcSECgiDPXFBRixcdCS9WOl1Zz9WYj9qNnlK6N8W9ut4/5mxLDfTdb3OTY0LBMAubPOXlT0QL2B87R/Mlooo7HC2Bps9AuJqHGAoKBCsPi+ny6xJe6IPWB0qwgu36mb03yKXM5zN/L+0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=HerHLKK5; arc=none smtp.client-ip=95.215.58.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="HerHLKK5" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=lrdTAluOUYWs62O0PpRF6nh/ALgtREIgbj5lfiADRdg=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787134581; v=1; x=1787739381; b=HerHLKK5iA7jemF1t+gQ978L4Z6+gpvBPttI933WycTGV7uSciIYX4Iguw7qtWWuJOy/K6J2 ZGE/Us7iRZjIX5CMzKVygkdn5mFDUBvYGE8AvC97sAuj0VzWTss9FuZm/bOeO/m9+upUaHau3TC Zi+I5n85Jw0OVzN2QNaB2i8Y= X-Envelope-To: linux-kernel@vger.kernel.org Received: from localhost (3.112.29.171) by mta12.migadu.com with ESMTPS id 572f4396708aeda8; Wed, 19 Aug 2026 10:16:21 +0000 X-Migadu-Flow: FLOW_OUT Date: Wed, 19 Aug 2026 18:16:13 +0800 From: Baoquan He To: kasong@tencent.com Cc: linux-mm@kvack.org, Andrew Morton , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Shakeel Butt , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Chris Li , Baolin Wang , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Yu Zhao , Zi Yan , Qi Zheng , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Kairui Song Subject: Re: [PATCH 5/7] mm/mglru: use explicit tier range in read_ctrl_pos() Message-ID: References: <20260818-mglru-flags-cleanup-v1-0-8dbbdac0d28c@tencent.com> <20260818-mglru-flags-cleanup-v1-5-8dbbdac0d28c@tencent.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260818-mglru-flags-cleanup-v1-5-8dbbdac0d28c@tencent.com> On 08/18/26 at 01:38pm, Kairui Song via B4 Relay wrote: > From: Kairui Song > > read_ctrl_pos() encodes the tier range in a single "tier" parameter > via "tier % MAX_NR_TIERS" as the start and "min(tier, MAX_NR_TIERS-1)" > as the end. This is hard to follow, maintain, or extend. Tier values > 0..3 select a single tier, while tier == MAX_NR_TIERS selects the > full range. > > Replace it with explicit (tier_min, tier_max) parameters using a > closed [tier_min, tier_max] interval, and add LRU_TIER_MIN and > LRU_TIER_MAX for the tier bounds. The call sites now become > self-documenting: > > - get_tier_idx: (LRU_TIER_MIN, LRU_TIER_MIN) for the first tier, > (tier, tier) for each subsequent tier > - get_type_to_scan: (LRU_TIER_MIN, LRU_TIER_MAX) for the full range > > No functional change. > > Signed-off-by: Kairui Song > --- > include/linux/mmzone.h | 2 ++ > mm/vmscan.c | 18 ++++++++++-------- > 2 files changed, 12 insertions(+), 8 deletions(-) To be honest, I like the old version better. The complexity is encapsulated inside the function, and tier_idx can reflect if it's operating on a specific tier or the whole tier. Anyway, this is also good: Reviewed-by: Baoquan He > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 32d9354a754f..d0b5c6217d25 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -492,6 +492,8 @@ enum lruvec_flags { > * folio->flags, masked by LRU_REFS_MASK. > */ > #define MAX_NR_TIERS 4U > +#define LRU_TIER_MIN 0U > +#define LRU_TIER_MAX (MAX_NR_TIERS - 1) > > #ifndef __GENERATING_BOUNDS_H > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index a819be6b7ae9..a613bb8d7271 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3198,8 +3198,8 @@ struct ctrl_pos { > int gain; > }; > > -static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, > - struct ctrl_pos *pos) > +static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min, > + int tier_max, int gain, struct ctrl_pos *pos) > { > int i; > struct lru_gen_folio *lrugen = &lruvec->lrugen; > @@ -3208,7 +3208,7 @@ static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, > pos->gain = gain; > pos->refaulted = pos->total = 0; > > - for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) { > + for (i = tier_min; i <= tier_max; i++) { > pos->refaulted += lrugen->avg_refaulted[type][i] + > atomic_long_read(&lrugen->refaulted[hist][type][i]); > pos->total += lrugen->avg_total[type][i] + > @@ -4804,9 +4804,9 @@ static int get_tier_idx(struct lruvec *lruvec, int type) > * This value is chosen because any other tier would have at least twice > * as many refaults as the first tier. > */ > - read_ctrl_pos(lruvec, type, 0, 2, &sp); > - for (tier = 1; tier < MAX_NR_TIERS; tier++) { > - read_ctrl_pos(lruvec, type, tier, 3, &pv); > + read_ctrl_pos(lruvec, type, LRU_TIER_MIN, LRU_TIER_MIN, 2, &sp); > + for (tier = LRU_TIER_MIN + 1; tier <= LRU_TIER_MAX; tier++) { > + read_ctrl_pos(lruvec, type, tier, tier, 3, &pv); > if (!positive_ctrl_err(&sp, &pv)) > break; > } > @@ -4827,8 +4827,10 @@ static int get_type_to_scan(struct lruvec *lruvec, int swappiness) > * Compare the sum of all tiers of anon with that of file to determine > * which type to scan. > */ > - read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp); > - read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv); > + read_ctrl_pos(lruvec, LRU_GEN_ANON, LRU_TIER_MIN, LRU_TIER_MAX, > + swappiness, &sp); > + read_ctrl_pos(lruvec, LRU_GEN_FILE, LRU_TIER_MIN, LRU_TIER_MAX, > + MAX_SWAPPINESS - swappiness, &pv); > > return positive_ctrl_err(&sp, &pv); > } > > -- > 2.55.0 > >