From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) (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 88AB220DD5C for ; Tue, 18 Mar 2025 14:10:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742307025; cv=none; b=N6YZhKilnCFapmaTkwwbRtIDsnRA3iaeimny5jZBRJCLwvqD3IVwWcY43lugEYA5NtIqvQuYRK4VPPNHyPY1upi/I2sSZ+NS9TH/ubhDA0oGBnJkA7WigApq8X588OOsAcyT//lsiSMRQ3ujYetHawM4VzPPOmdjVWcJCj4MHHQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742307025; c=relaxed/simple; bh=L/s03vrxGi8wDre+KKeUbgbJXRYK5FL3hEEpvhZlSsY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jFE40Kr/bFY2sDbkZ3ZWY/glT67PQQbUn9HvXZIjxbWcETC/mQucITpPB4p0aZx/Mch0oDQ13vKjeo4dZ3dFh22XkkuTGyScq7RhqRmrgTS1MH00zBtJHtxfmWBw/2RGbmfGjBP8RTY7T4AgH1YdXRV1fRUMd9y3ESlMoE/swUI= 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=lAAaoRY/; arc=none smtp.client-ip=91.218.175.173 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="lAAaoRY/" Date: Tue, 18 Mar 2025 14:10:15 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1742307020; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/yh8Ym+ECWzQ1Tx2CMjrE4Vg5wnvaSOPbsBq3IpvaIM=; b=lAAaoRY/wdVvq+G5Z0aQ7RPljrBAVKz4psTXspaaz8OHii4FtoiNVPOZxKTRmMJ0SrGVEt fHIaAePt57dmK905b/oRE98zXZj9HkQeTgHlPpH/Vjc0dM7e+NcSvufkBHsrRLjbCwL3ea t6v9oec4XFwNH1m2yedXc7gOY6zu2Is= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yosry Ahmed To: Zhongkun He Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, yuzhao@google.com, mhocko@suse.com, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: add swappiness=max arg to memory.reclaim for only anon reclaim Message-ID: References: <20250318135330.3358345-1-hezhongkun.hzk@bytedance.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: <20250318135330.3358345-1-hezhongkun.hzk@bytedance.com> X-Migadu-Flow: FLOW_OUT On Tue, Mar 18, 2025 at 09:53:30PM +0800, Zhongkun He wrote: > With this patch 'commit <68cd9050d871> ("mm: add swappiness= arg to > memory.reclaim")', we can submit an additional swappiness= argument > to memory.reclaim. It is very useful because we can dynamically adjust > the reclamation ratio based on the anonymous folios and file folios of > each cgroup. For example,when swappiness is set to 0, we only reclaim > from file folios. > > However,we have also encountered a new issue: when swappiness is set to > the MAX_SWAPPINESS, it may still only reclaim file folios. > > So, we hope to add a new arg 'swappiness=max' in memory.reclaim where > proactive memory reclaim only reclaims from anonymous folios when > swappiness is set to max. The swappiness semantics from a user > perspective remain unchanged. > > For example, something like this: > > echo "2M swappiness=max" > /sys/fs/cgroup/memory.reclaim > > will perform reclaim on the rootcg with a swappiness setting of 'max' (a > new mode) regardless of the file folios. Users have a more comprehensive > view of the application's memory distribution because there are many > metrics available. For example, if we find that a certain cgroup has a > large number of inactive anon folios, we can reclaim only those and skip > file folios, because with the zram/zswap, the IO tradeoff that > cache_trim_mode or other file first logic is making doesn't hold - > file refaults will cause IO, whereas anon decompression will not. > > With this patch, the swappiness argument of memory.reclaim has a new > mode 'max', means reclaiming just from anonymous folios both in traditional > LRU and MGLRU. Is MGLRU handled in this patch? > > Here is the previous discussion: > https://lore.kernel.org/all/20250314033350.1156370-1-hezhongkun.hzk@bytedance.com/ > https://lore.kernel.org/all/20250312094337.2296278-1-hezhongkun.hzk@bytedance.com/ > > Suggested-by: Yosry Ahmed > Signed-off-by: Zhongkun He > --- > Documentation/admin-guide/cgroup-v2.rst | 4 ++++ > include/linux/swap.h | 4 ++++ > mm/memcontrol.c | 5 +++++ > mm/vmscan.c | 10 ++++++++++ > 4 files changed, 23 insertions(+) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index cb1b4e759b7e..c39ef4314499 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1343,6 +1343,10 @@ The following nested keys are defined. > same semantics as vm.swappiness applied to memcg reclaim with > all the existing limitations and potential future extensions. > > + If set swappiness=max, memory reclamation will exclusively > + target the anonymous folio list for both traditional LRU and > + MGLRU reclamation algorithms. > + I don't think we need to specify LRU and MGLRU here. What about: Setting swappiness=max exclusively reclaims anonymous memory. > memory.peak > A read-write single value file which exists on non-root cgroups. > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index b13b72645db3..a94efac10fe5 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -419,6 +419,10 @@ extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > #define MEMCG_RECLAIM_PROACTIVE (1 << 2) > #define MIN_SWAPPINESS 0 > #define MAX_SWAPPINESS 200 > + > +/* Just recliam from anon folios in proactive memory reclaim */ > +#define ONLY_ANON_RECLAIM_MODE (MAX_SWAPPINESS + 1) > + This is a swappiness value so let's keep that clear, e.g. SWAPPINESS_ANON_ONLY or similar. > extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, > unsigned long nr_pages, > gfp_t gfp_mask, > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 4de6acb9b8ec..0d0400f141d1 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4291,11 +4291,13 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of, > > enum { > MEMORY_RECLAIM_SWAPPINESS = 0, > + MEMORY_RECLAIM_ONLY_ANON_MODE, > MEMORY_RECLAIM_NULL, > }; > > static const match_table_t tokens = { > { MEMORY_RECLAIM_SWAPPINESS, "swappiness=%d"}, > + { MEMORY_RECLAIM_ONLY_ANON_MODE, "swappiness=max"}, MEMORY_RECLAIM_SWAPPINESS_MAX? > { MEMORY_RECLAIM_NULL, NULL }, > }; > > @@ -4329,6 +4331,9 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, > if (swappiness < MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS) > return -EINVAL; > break; > + case MEMORY_RECLAIM_ONLY_ANON_MODE: > + swappiness = ONLY_ANON_RECLAIM_MODE; > + break; > default: > return -EINVAL; > } > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c767d71c43d7..779a9a3cf715 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2438,6 +2438,16 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, > goto out; > } > > + /* > + * Do not bother scanning file folios if the memory reclaim > + * invoked by userspace through memory.reclaim and set > + * 'swappiness=max'. > + */ /* Proactive reclaim initiated by userspace for anonymous memory only */ > + if (sc->proactive && (swappiness == ONLY_ANON_RECLAIM_MODE)) { Do we need to check sc->proactive here? Supposedly this swappiness value can only be passed in from proactive reclaim. Instead of silently ignoring the value from other paths, I wonder if we should WARN on !sc->proactive instead. > + scan_balance = SCAN_ANON; > + goto out; > + } > + > /* > * Do not apply any pressure balancing cleverness when the > * system is close to OOM, scan both anon and file equally > -- > 2.39.5 >