From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) (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 551964499A4 for ; Sat, 11 Jul 2026 09:18:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783761482; cv=none; b=lND68RMXlnsq3TZw0YB7zAXxe6IA3uEaQY8nq4FBIeCwmaw32spc2ijZDsrKGf5lsslW11xKSCiHkMYNNpHXGcvnD7LQXoD6nsUxIkzyZ+oc6kzEJ4DBMDer0qr7Xyw/hsUn2H+VZWgC+gYnJ7GvTYc4Xl53/kx50YA6AA2K//E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783761482; c=relaxed/simple; bh=xrlq+7wzhdReBl+QQeyHVjagVI78GJXwCjCYRc/XiEY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OHPQ4q6OrMBqtaDPrJp8Vdphwy6dl54knoQHmzPr+Hyt76Iatxn+Ghjlrod5bKZM+AkaIcVTT8ggLRpqeeLCUmTh1P8ZBZj9fQZSx+h78Zq/MCD7pzOmOa1n8cp1KLD6uXBykbU2JC0cTWQIBmgj3pivj20/YfJva4acYaNhsxo= 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=d+Asd+6Q; arc=none smtp.client-ip=95.215.58.172 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="d+Asd+6Q" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783761478; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KkBQdQqW9l/vkDYfka0IKWJdPmtoY2v3nYkEf3NdSrc=; b=d+Asd+6Q4RHoaNC1k4UuSAQh6JkxcKjIkj6+0umPOhRLz62ERK8kdLcfL2hQO/TP7oatHc IE69EkW/tg/GGFYQpoceI9SUAQ858KEUzl1Y6OsFIUv9KKuDJ5K36IgX9IvUGdqwfMKqvX B4mlE2stVO0JCse0GTDPHYFAUgNOLjM= Date: Sat, 11 Jul 2026 17:17:35 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH -next] memcg: move mem_cgroup_swappiness to memcontrol.h To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton , Chris Li , Kairui Song Cc: Muchun Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ridong Chen References: <20260710111224.2355668-1-ridong.chen@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ridong Chen In-Reply-To: <20260710111224.2355668-1-ridong.chen@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 7/10/2026 7:12 PM, Ridong wrote: > From: Ridong Chen > > The per-memcg swappiness knob is v1-only; v2 always uses global > vm_swappiness and ignores the per-cgroup field. > > Guard memcg->swappiness with CONFIG_MEMCG_V1, and move the helper > to memcontrol.h where it belongs. > > No functional change for v1; v2-only kernels drop the unused field. > > Signed-off-by: Ridong Chen > --- > include/linux/memcontrol.h | 25 +++++++++++++++++++++++-- > include/linux/swap.h | 19 ------------------- > mm/memcontrol.c | 3 +-- > 3 files changed, 24 insertions(+), 23 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index e1f46a0016fc..f59614956f96 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -239,8 +239,6 @@ struct mem_cgroup { > */ > bool oom_group; > > - int swappiness; > - > /* memory.events and memory.events.local */ > struct cgroup_file events_file; > struct cgroup_file events_local_file; > @@ -318,6 +316,9 @@ struct mem_cgroup { > /* List of events which userspace want to receive */ > struct list_head event_list; > spinlock_t event_list_lock; > + > + int swappiness; > + > #endif /* CONFIG_MEMCG_V1 */ > > struct mem_cgroup_per_node *nodeinfo[]; > @@ -365,6 +366,9 @@ enum objext_flags { > > #define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1) > > +/* Defined in mm/vmscan.c; used by mem_cgroup_swappiness(). */ > +extern int vm_swappiness; > + > #ifdef CONFIG_MEMCG > /* > * After the initialization objcg->memcg is always pointing at > @@ -1440,6 +1444,23 @@ static inline void mem_cgroup_flush_workqueue(void) { } > static inline int mem_cgroup_init(void) { return 0; } > #endif /* CONFIG_MEMCG */ > > +static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) > +{ > +#ifdef CONFIG_MEMCG_V1 > + /* Cgroup2 doesn't have per-cgroup swappiness */ > + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + return READ_ONCE(vm_swappiness); > + > + /* root ? */ > + if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > + return READ_ONCE(vm_swappiness); > + > + return READ_ONCE(memcg->swappiness); > +#else > + return READ_ONCE(vm_swappiness); > +#endif > +} > + > /* > * Extended information for slab objects stored as an array in page->memcg_data > * if MEMCG_DATA_OBJEXTS is set. > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 3f31b6a56788..f27e73f29195 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -366,7 +366,6 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem, > pg_data_t *pgdat, > unsigned long *nr_scanned); > extern unsigned long shrink_all_memory(unsigned long nr_pages); > -extern int vm_swappiness; > long remove_mapping(struct address_space *mapping, struct folio *folio); > > #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) > @@ -530,25 +529,7 @@ static inline int add_swap_extent(struct swap_info_struct *sis, > } > #endif /* CONFIG_SWAP */ > #ifdef CONFIG_MEMCG > -static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) > -{ > - /* Cgroup2 doesn't have per-cgroup swappiness */ > - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > - return READ_ONCE(vm_swappiness); > - > - /* root ? */ > - if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) > - return READ_ONCE(vm_swappiness); > - > - return READ_ONCE(memcg->swappiness); > -} > - > void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid); > -#else > -static inline int mem_cgroup_swappiness(struct mem_cgroup *mem) > -{ > - return READ_ONCE(vm_swappiness); > -} > #endif > > #if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 938f190a98fe..2d659b76cd77 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4174,11 +4174,10 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) > #endif > page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); > if (parent) { > - WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); > - > page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl); > page_counter_init(&memcg->swap, &parent->swap, false); > #ifdef CONFIG_MEMCG_V1 > + WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); > memcg->memory.track_failcnt = !memcg_on_dfl; > WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable)); > page_counter_init(&memcg->kmem, &parent->kmem, false); I have resent this patch [1], as I found another issue related to it. [1] https://lore.kernel.org/linux-mm/20260711091157.306070-1-ridong.chen@linux.dev/ -- Best regards, Ridong