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 3E35C3CC7EB for ; Wed, 15 Jul 2026 08:28:21 +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=1784104102; cv=none; b=LzwG+7orfNMgKvy2qHGFNKehfw2FZomcniNlYs2SvbIaTP1SYwmc5GwLKxwXgy1HLRSiHQeTAX57qKfeUA/iln9JqHWR4dUlBU55owV2qgXbkGGU10UiXrBnKd+rwCfuS40pMWgmOZ4mLwQCSOw/3AjYPhtUCDx9sm6JagQHwWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784104102; c=relaxed/simple; bh=3cK/hdA+KmShv1b5t2wupekU05qRjUP2fy2Qsp/AljI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hWhJyX6XkmMEUogT5oGIspupvrvWRUf3XQ/i+CEQH8D5TCtYcpZIuRox1AtoFbFKhni8dLCHuvSSqytkYSM9F4NH6s8KZLNshis0oqZ76Ttp5MrfQh7L1HbZGCrmBZeQNneCFYal83bF/OqzGOIR/KLpeMdPEDxCjLr4eBlhwcU= 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=FRUJElK8; 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="FRUJElK8" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784104098; 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=S7GAdy7BzpH1mY1l3xxBJ7jnUWvRdOJWdWyYoP9VmOo=; b=FRUJElK8nJYnUa4z0EhRgh9pD4xudbHVG3EKKJQ9g0U+5ekiB4AaVTzUiDhJzu5yXkV09b m4Qq3bCA8Dx2hgQRlhUB1y35ui00PREwKAYGVnsbdExx+jHbEUkfLQ72XPj2Sr9CTPpiG8 oHPr5rTYCpbKDSkbrAbbhwRu+SS7YHk= Date: Wed, 15 Jul 2026 16:28:04 +0800 Precedence: bulk X-Mailing-List: linux-kernel@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> <0545ee70-b0a0-4a93-ac2c-3e84ff504e5a@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 9:46 PM, Barry Song wrote: > On Tue, Jul 14, 2026 at 7:31 PM Ridong Chen wrote: > > [...] >>>>>> >>>>>> 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. >>> >>> Either mm/swap.h or mm/internal.h. >>> vm_swappiness probably belongs in mm/swap.h rather than >>> mm/internal.h, right? >>> >>> BTW, I am not particularly eager about this cleanup; >>> it could be done later as a separate patch. >>> >>> If you decide not to do the cleanup, I think it would be better to >>> leave "extern int vm_swappiness" in include/linux/swap.h rather than >>> declaring it in include/linux/memcontrol.h? >> I noticed that some swap-related macros are already defined in >> mm/internal.h, so I'm planning to place the code right after them for >> better grouping. Does that work for you? > > We also have mm/swap.h, which is dedicated to exporting > swap-related things. Is it a better place than mm/internal.h? > Placing it in mm/swap.h is fine with me. Will update. ``` --- a/mm/swap.h +++ b/mm/swap.h @@ -4,6 +4,7 @@ #include /* for atomic_long_t */ #include /* for PAGE_SHIFT */ +#include struct mempolicy; struct swap_iocb; struct swap_memcg_table; @@ -76,6 +77,25 @@ enum swap_cluster_flags { CLUSTER_FLAG_MAX, }; +extern int vm_swappiness; + +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 +} + ``` -- Best regards Ridong