From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (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 E0E182FFFB7 for ; Mon, 22 Dec 2025 03:55:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766375733; cv=none; b=EsrZvgnVst0S+YOflYbCmL5qdlXt4ri4Ljrx2mP6ctdRPFln1/wClIIaopXDaQy5IYpF/kLliA77myvLBiN8TZKai6KzR25voYsvSlzh37pRw4ZCFvPkbmk4cM7FRJj+l8+Mw4lQ/0cyrqGmD7+Ydr+FFMAcm3dw5AdIyXZdei4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766375733; c=relaxed/simple; bh=nnyyMxSWT32A67WXcmIC2RNVzPXhPhejgXkyfW5jcHE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=T9yjONvJwzFiTG6NFQAtF7oCTFodGl8/56Z4ZXHpgdep1c8LtruWlf9Ez6JSJc94a/ZIq8NZXNdPmNKyZ+SXLxPWePMdBBqlHXL4I17l3VvznynpN0cTMiQzDSV63mPctwGuWgYXNM4/BAEEuUeQZ+IV0vLrAoxxx9+lMyEwq2w= 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=Y5bED2PI; arc=none smtp.client-ip=91.218.175.184 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="Y5bED2PI" Message-ID: <00f47523-e458-4e9e-8354-1c33bf0591b8@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766375715; 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=2xqiag8fioZOe9NX9oHRHaDgP//h6CBY1O8QvNdZ/XU=; b=Y5bED2PIdjRswHhz5ri86a3xuzcsAPrgnCBsf4HQ2FgRrsukkrTd76VX+FYh4x8wwvB3mB Fp0g52FAQ4i9IXYKS3Wfsv3Z/gRuJqfBuAroC+gLllj/yblELd8z0vYQDuJxl3RR9vHMIb vIkXAJSjU0i86jfI3sXnHuPHndBX8mM= Date: Mon, 22 Dec 2025 11:55:01 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2 24/28] mm: vmscan: prepare for reparenting traditional LRU folios To: Johannes Weiner Cc: hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng References: <800faf905149ee1e1699d9fd319842550d343f43.1765956026.git.zhengqi.arch@bytedance.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 12/18/25 9:32 PM, Johannes Weiner wrote: > On Wed, Dec 17, 2025 at 03:27:48PM +0800, Qi Zheng wrote: >> From: Qi Zheng >> >> To reslove the dying memcg issue, we need to reparent LRU folios of child > > resolve Got it. > >> memcg to its parent memcg. For traditional LRU list, each lruvec of every >> memcg comprises four LRU lists. Due to the symmetry of the LRU lists, it >> is feasible to transfer the LRU lists from a memcg to its parent memcg >> during the reparenting process. >> >> This commit implements the specific function, which will be used during >> the reparenting process. >> >> Signed-off-by: Qi Zheng >> Reviewed-by: Harry Yoo > > Overall looks sane to me. I have a few nits below, not nothing > major. With those resolved, please feel free to add > > Acked-by: Johannes Weiner Thanks! > >> @@ -2648,6 +2648,44 @@ static bool can_age_anon_pages(struct lruvec *lruvec, >> lruvec_memcg(lruvec)); >> } >> >> +#ifdef CONFIG_MEMCG >> +static void lruvec_reparent_lru(struct lruvec *src, struct lruvec *dst, >> + enum lru_list lru) >> +{ >> + int zid; >> + struct mem_cgroup_per_node *mz_src, *mz_dst; >> + >> + mz_src = container_of(src, struct mem_cgroup_per_node, lruvec); >> + mz_dst = container_of(dst, struct mem_cgroup_per_node, lruvec); >> + >> + if (lru != LRU_UNEVICTABLE) >> + list_splice_tail_init(&src->lists[lru], &dst->lists[lru]); >> + >> + for (zid = 0; zid < MAX_NR_ZONES; zid++) { >> + mz_dst->lru_zone_size[zid][lru] += mz_src->lru_zone_size[zid][lru]; >> + mz_src->lru_zone_size[zid][lru] = 0; >> + } >> +} >> + >> +void lru_reparent_memcg(struct mem_cgroup *src, struct mem_cgroup *dst) > > I can see why you want to pass both src and dst for convenience, but > it makes the API look a lot more generic than it is. It can only > safely move LRUs from a cgroup to its parent. > > As such, I'd slightly prefer only passing one pointer and doing the > parent lookup internally. It's dealer's choice. Make sense, will do. > > However, if you'd like to keep both pointers for a centralized lookup, > can you please rename the parameters @child and @parent, and add > > VM_WARN_ON(parent != parent_mem_cgroup(child)); > > Also please add a comment explaining the expected caller locking. OK. > > Lastly, vmscan.c is the reclaim policy. Mechanical LRU shuffling like > this is better placed in mm/swap.c. OK, will move it to mm/swap.c.