From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f169.google.com (mail-pf1-f169.google.com [209.85.210.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8AD3215624D for ; Wed, 24 Sep 2025 10:06:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758708391; cv=none; b=cDXAcTEUk4lELdKy5R+hmCTptCjXdWYzmzxu75iBbicw070JZ4nl+5AaIFQP/nG1m4rj9m6lhQrKwtYBUGhqF5Eu5S5x19gXybDklUjYepZJDIpD7qai+0dNRksuosUBglvzwIMioXlXJkKK+kAb/23WIkOWLr0sWel6TVoIqYg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758708391; c=relaxed/simple; bh=U4NgULEgdH3+wVK2A6tyf0ydUVdvgU3xgFrasX8sbIc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rEv9SyioHVAsT/qVry1b86vEqXY4w8swHnUyzMeWq90G2CkHn5AM08tAoVAsaxc8+4Ev/Pv3AEYWQlphGiCcoCY968E4KxDnfTOgtfE3d+A6hSH0wefjXDt0F1CtdSRP2C5TFH+4EpQ1pcQlGgDM/1nY+A2U8Xnxe2em4KosO3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=PgQdGmnK; arc=none smtp.client-ip=209.85.210.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="PgQdGmnK" Received: by mail-pf1-f169.google.com with SMTP id d2e1a72fcca58-7704f3c46ceso6211603b3a.2 for ; Wed, 24 Sep 2025 03:06:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1758708386; x=1759313186; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=EfE2mgVlyr7iNmaZ4vQXyrWE/ZvZPrZL7XGUEK7ATPc=; b=PgQdGmnK5nIVXYhMWW3bI7kcM88aqLrVQiCm3VpCZ9kfz8ppcHGXAyhT6/mkg80kjn u6oU3JVrexWEB1xJ+/VAkup5Itikih+4zPfW7MnxssX6xUOdoqBCLee5NdTqBP6hZkNs fiT9SwLkG4I1c/nxntfjl2bD5qDT4FHWXQDqDZHpzYT6YFMCriCogOV8lew/7cC0sGuk dn3u7AENDoe++ZI7OCRTInsiOwlM/owEc3ubmxy5m0pUFYp1lIsOpJq/Cz3mZ99hS0T4 lRAfWgPrMmKXgjTFve76jY63yDCobpe4E/7kFv0BXWC/qbNH+sIRL3UU5XD5bTXRB8Td G82w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758708386; x=1759313186; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=EfE2mgVlyr7iNmaZ4vQXyrWE/ZvZPrZL7XGUEK7ATPc=; b=xB6KB6g2tMl+K67DdyNHgLAbUoZZS3LMy5NXK7+Fs/3MVoXsMozi5YLUpGzanwrfbJ j7czfEsSKm5IFZEzb4RCkB6nJDDaoJX/c6Jd4qdRso8kE8+NI8qRhaa/7nQ8F6OQgMEh ZoXJRDjKPcU2Bb/TA/OIKSLHDj4YPqAVe3b6PmjCe43Q1EpSjZO6FA6ft16Yx0+g/Tnz 4Oud/DNq7xm+BinuxDn9RqmHnmXw+KIyshhEWZIyNVv+SYcPuaOaDWvTGVdTYsqb8Ose yZBFnnkHLezb+GP9Qh2NQW0EhMPJMj3BgLOBWzuZQFLVUSjD1RbhaimwtmQjr7jUjsjS tlAA== X-Forwarded-Encrypted: i=1; AJvYcCW55q5gYLiUy1XC+4gQ9CSfAdZe8G8osDN8SPrLfQsX5jH2hksdHJBpek+ryWLNU2DvB9v7pcfZbAmZwio=@vger.kernel.org X-Gm-Message-State: AOJu0Yw0FF+WxeIqgQ2QexBwVHh0hBpndaByjXeZmKPT2/0JFYmrqlUy eSyY01BsaID6cNtuHF/kGAzV5UxyJYhDZZz6+2Xiu83jG/M+815EDiJIi168Ddt4g80= X-Gm-Gg: ASbGncvPJwHav4oI2hdcGk8rNj8dxIzrvPnuKOdJ3HMbtJiBjOqdfMqAWHR+rWh4CjM hcYW/H7N+HacD8kRpcTC0ToBBBxn7voIvWMaCJqIJeOE1/knGLDF4eKsYLewq8HVgqOweoRxYlB XhygNkhroe+21JRmVgXk7xFW5GFJKujQroY2GMPQBGcIiM9CBMqszkOnDfgAETIXp4x3quKbXDp GVyu5vhW07sMNK8fKOu4d1zyzysIb2BF+TzLjFxUN/2/SCEdABt0BG1DjOTdFMSyaStb8ki+JrN e302ttaoSWS4Nd3VBXdKyA2H9tx/1j1jhWzhUEs1nHSlfpCkVL1/20B/Kp0NL6HTie+TWE9iWU+ 69SR2MPvu8DbpAS6xS5mRmdtHJ0Rhasxrp6djdObRugqfdJK8CjONu9iGzE5zKoSoDHD3 X-Google-Smtp-Source: AGHT+IFhsnsZYVlejzedhp8ryD+eY+C2FjhYDyPffnI2uMukcLjw9DOqyDy7/D84SWZQ/6CRngyUhw== X-Received: by 2002:a05:6a00:1990:b0:77f:1a7e:7bc0 with SMTP id d2e1a72fcca58-77f53acfa71mr6945066b3a.31.1758708385394; Wed, 24 Sep 2025 03:06:25 -0700 (PDT) Received: from [100.82.90.25] ([63.216.146.178]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-77f0da43089sm13920289b3a.90.2025.09.24.03.06.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Sep 2025 03:06:24 -0700 (PDT) Message-ID: <72d23e4d-6c59-4adf-86ba-aa3ae8566bde@bytedance.com> Date: Wed, 24 Sep 2025 18:06:14 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/4] mm: thp: reparent the split queue during memcg offline To: Roman Gushchin Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, shakeel.butt@linux.dev, muchun.song@linux.dev, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <55370bda7b2df617033ac12116c1712144bb7591.1758618527.git.zhengqi.arch@bytedance.com> <7ia4bjn06w62.fsf@castle.c.googlers.com> From: Qi Zheng In-Reply-To: <7ia4bjn06w62.fsf@castle.c.googlers.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Roman, On 9/24/25 5:23 PM, Roman Gushchin wrote: > Qi Zheng writes: > >> In the future, we will reparent LRU folios during memcg offline to >> eliminate dying memory cgroups, which requires reparenting the split queue >> to its parent. > > Nit: commit logs should really focus on the actual change, not the future > plans. Got it. > >> >> Similar to list_lru, the split queue is relatively independent and does >> not need to be reparented along with objcg and LRU folios (holding >> objcg lock and lru lock). So let's apply the same mechanism as list_lru >> to reparent the split queue separately when memcg is offine. >> >> Signed-off-by: Qi Zheng >> --- >> include/linux/huge_mm.h | 2 ++ >> include/linux/mmzone.h | 1 + >> mm/huge_memory.c | 39 +++++++++++++++++++++++++++++++++++++++ >> mm/memcontrol.c | 1 + >> mm/mm_init.c | 1 + >> 5 files changed, 44 insertions(+) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index f327d62fc9852..a0d4b751974d2 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -417,6 +417,7 @@ static inline int split_huge_page(struct page *page) >> return split_huge_page_to_list_to_order(page, NULL, ret); >> } >> void deferred_split_folio(struct folio *folio, bool partially_mapped); >> +void reparent_deferred_split_queue(struct mem_cgroup *memcg); >> >> void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, >> unsigned long address, bool freeze); >> @@ -611,6 +612,7 @@ static inline int try_folio_split(struct folio *folio, struct page *page, >> } >> >> static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {} >> +static inline void reparent_deferred_split_queue(struct mem_cgroup *memcg) {} >> #define split_huge_pmd(__vma, __pmd, __address) \ >> do { } while (0) >> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index 7fb7331c57250..f3eb81fee056a 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -1346,6 +1346,7 @@ struct deferred_split { >> spinlock_t split_queue_lock; >> struct list_head split_queue; >> unsigned long split_queue_len; >> + bool is_dying; >> }; >> #endif >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 48b51e6230a67..de7806f759cba 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1094,9 +1094,15 @@ static struct deferred_split *folio_split_queue_lock(struct folio *folio) >> struct deferred_split *queue; >> >> memcg = folio_memcg(folio); >> +retry: >> queue = memcg ? &memcg->deferred_split_queue : >> &NODE_DATA(folio_nid(folio))->deferred_split_queue; >> spin_lock(&queue->split_queue_lock); >> + if (unlikely(queue->is_dying == true)) { >> + spin_unlock(&queue->split_queue_lock); >> + memcg = parent_mem_cgroup(memcg); >> + goto retry; >> + } >> >> return queue; >> } >> @@ -1108,9 +1114,15 @@ folio_split_queue_lock_irqsave(struct folio *folio, unsigned long *flags) >> struct deferred_split *queue; >> >> memcg = folio_memcg(folio); >> +retry: >> queue = memcg ? &memcg->deferred_split_queue : >> &NODE_DATA(folio_nid(folio))->deferred_split_queue; >> spin_lock_irqsave(&queue->split_queue_lock, *flags); >> + if (unlikely(queue->is_dying == true)) { >> + spin_unlock_irqrestore(&queue->split_queue_lock, *flags); >> + memcg = parent_mem_cgroup(memcg); >> + goto retry; >> + } >> >> return queue; >> } >> @@ -4284,6 +4296,33 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, >> return split; >> } >> >> +void reparent_deferred_split_queue(struct mem_cgroup *memcg) >> +{ >> + struct mem_cgroup *parent = parent_mem_cgroup(memcg); >> + struct deferred_split *ds_queue = &memcg->deferred_split_queue; >> + struct deferred_split *parent_ds_queue = &parent->deferred_split_queue; >> + int nid; >> + >> + spin_lock_irq(&ds_queue->split_queue_lock); >> + spin_lock_nested(&parent_ds_queue->split_queue_lock, SINGLE_DEPTH_NESTING); >> + >> + if (!ds_queue->split_queue_len) >> + goto unlock; >> + >> + list_splice_tail_init(&ds_queue->split_queue, &parent_ds_queue->split_queue); >> + parent_ds_queue->split_queue_len += ds_queue->split_queue_len; >> + ds_queue->split_queue_len = 0; >> + /* Mark the ds_queue dead */ >> + ds_queue->is_dying = true; >> + >> + for_each_node(nid) >> + set_shrinker_bit(parent, nid, shrinker_id(deferred_split_shrinker)); > > Does this loop need to be under locks? I think it is not necessary, but the loop overhead should not be high. > >> + >> +unlock: >> + spin_unlock(&parent_ds_queue->split_queue_lock); >> + spin_unlock_irq(&ds_queue->split_queue_lock); >> +} >> + >> #ifdef CONFIG_DEBUG_FS >> static void split_huge_pages_all(void) >> { >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index e090f29eb03bd..d03da72e7585d 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -3887,6 +3887,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) >> zswap_memcg_offline_cleanup(memcg); >> >> memcg_offline_kmem(memcg); >> + reparent_deferred_split_queue(memcg); >> reparent_shrinker_deferred(memcg); > > I guess the naming can be a bit more consistent here :) Do you mean to change them all to: memcg_offline_xxx() or reparent_xxx() ? Thanks, Qi > > Thanks!