From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (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 D487A3D9DB6 for ; Tue, 14 Jul 2026 07:43:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784014996; cv=none; b=Tw3/hY1YmkjsL+EZi3ii3ClGq7KgTQ5+vdRip0HqE2V05KljygLmSbZacuRNkZ1/c6BnL/HuvMmsLgBbJETH4iMti8l525M/VYlzkitdD6sX3GIav0vstg84MOUu/5d1dsvVKsz076paYRN8Wc3tL1mT65Dt66wwXwbPmC/x40Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784014996; c=relaxed/simple; bh=2CTl+A7c2f3UrWnkcWruNPzMdTHee/XegWULNb/RA/4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DATz6pCnBz1kQxCtSf/8RjzIcS/OafnFqOODoYGa3/KaE0SnRlpYvOuJcUP+Zw1PrvyD6E3lBCWnYuyse9Ha2W2FKcP+KcFCetDxBn4PgPhBcxUYAmlDJcLXWg5zTuL93gRoWS0uDN0BM6iRQGIk6Bm66KdBssbDJQBaIh8BUrE= 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=hT0bmfKP; arc=none smtp.client-ip=91.218.175.177 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="hT0bmfKP" Message-ID: <0545ee70-b0a0-4a93-ac2c-3e84ff504e5a@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784014992; 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=f0I0BJ125x0ILzpKQzbAIfOkMzFcIP5uJz7O94Fnv8U=; b=hT0bmfKPqQc9pDzFwsqCmtPPFoWQhN08bP7XCztt6T6O9I/sjqP6TCj1HVTvHABehMC/sC D5UK+iM2oYcDiV2UGmsSH4Db3ghqh9VfT3omemPDv4Yqjxh37MZa9Q3ToX9mJG0B4UETN7 atCNfg0O9qKFcAuPjlda6yCvqWeDXv4= Date: Tue, 14 Jul 2026 15:42:52 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 1/2] memcg: move mem_cgroup_swappiness to memcontrol.h To: Barry Song Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Chris Li , Kairui Song , David Hildenbrand , Yuanchu Xie , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Ridong Chen References: <20260711091157.306070-1-ridong.chen@linux.dev> <20260711091157.306070-2-ridong.chen@linux.dev> <87dc4105-b98b-4541-bafe-c0adfbf58836@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ridong Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 7/14/2026 9:48 AM, Barry Song wrote: > On Tue, Jul 14, 2026 at 9:43 AM Barry Song wrote: >> >> On Tue, Jul 14, 2026 at 9:20 AM Ridong Chen wrote: >>> >>> >>> >>> On 7/13/2026 11:08 PM, Barry Song wrote: >>>> On Sat, Jul 11, 2026 at 5:12 PM Ridong Chen 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 >>>>> Acked-by: Johannes Weiner >>>> >>>> Reviewed-by: Barry Song >>>> >>>> With some nits. >>>> >>>>> --- >>>> [...] >>>>> 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; >>>> >>>> This is a bit unusual. I'm not sure whether mm/swap.h would be >>>> a more appropriate place for this. >>>> >>> Thank you for your reply. >>> >>> The vm_swappiness variable is not utilized within mm/swap.c. >>> Furthermore, since memcontrol.h does not include swap.h, retaining the >>> extern int vm_swappiness declaration in mm/swap.h will result in a >>> compilation failure. >> >> If this is the case, it still seems better to keep >> extern int vm_swappiness in include/linux/swap.h. >> >> Then we don't need the comment: >> /* Defined in mm/vmscan.c; used by mem_cgroup_swappiness(). */ >> >> It also makes it clearer that vm_swappiness is an extern variable >> belonging to the swap module, rather than the memcontrol module. > > BTW, if mem_c_group_swappiness() and vm_swappiness are only used > within mm/, could all of these be moved to mm/swap.h and > mm/internal.h instead? > > We are making a big effort to move many unrelated things out of > include/linux/swap.h recently. Could you check? > > https://lore.kernel.org/linux-mm/20260708-ch-swap-series-plus-folio-lru-cleanup-v9-0-2bc72b4f8730@gmail.com/ Good suggestion. Moving them to mm/internal.h makes sense. Will update in the next version. -- Best regards Ridong