From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-108.mta1.migadu.com [95.215.58.108]) (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 673AB22D4E9 for ; Tue, 18 Aug 2026 04:32:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787027572; cv=none; b=UX9wU0nLehgV/lMW9dK+7xdDY/755H5aoEu51cdPq5anTy7Hn62+PlUw4GaNp+hKG5sIE8JOqrd6XSEY37sWR/3fTqevNyRpb+570r3uqk1cC5+tKCc5Txv2rBOP9HPbTvoZo7Kc5VvUQHxdEUpYGqVn+TrJujryXAyHv4faeUA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787027572; c=relaxed/simple; bh=0Aeu40CJPGg7YRxdQERUwajbl2h/m9U4sdY8I6B0VYI=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=JgLwO8OhgQ0DaoRvfUO9lVOQgcFlEw3yEUzS8zqqtQjiOmZXcJ+0AzhQMX5BPnVbfeDeBXZxQojD/YmsaAIPB0pPGfihgKss7TK9UDin0lS0sMZ279cG5oTCpkoVnJILwhbUiDB3+33QK1udsNRnMW7701q63v0AlBO1PoSrryA= 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=HGopUP2/; arc=none smtp.client-ip=95.215.58.108 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="HGopUP2/" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=0Aeu40CJPGg7YRxdQERUwajbl2h/m9U4sdY8I6B0VYI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787027568; v=1; x=1787632368; b=HGopUP2/F+uKWqEig+66rbj55FW/4Xtb8zqBR+V2aGujRikZ2ewOGYV9sx/X8N9KGevlIVUu MGdMSBdjJ+17Ywi8DG5DDHUrbJVU1faCC9+A8sb+dO1wZHDek4cpq9Ks0w9hLcTmkKPS9odE8gb q8GDUp8QhNWf2IJfZUVgleOo= X-Envelope-To: linux-kernel@vger.kernel.org Received: from [192.168.110.173] (223.70.160.239) by smtp.migadu.com with ESMTPS id 7e9ddfa9cc62e64c; Tue, 18 Aug 2026 04:32:48 +0000 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Tue, 18 Aug 2026 12:32:42 +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 Cc: cui.tao@linux.dev, tj@kernel.org, mkoutny@suse.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 4/8] mm/memcontrol: add per-tier charge and uncharge To: liuqiqi@kylinos.cn, linux-mm@kvack.org References: <20260818023121.100613-1-liuqiqi@kylinos.cn> <20260818023121.100613-5-liuqiqi@kylinos.cn> From: Tao Cui In-Reply-To: <20260818023121.100613-5-liuqiqi@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi,Qiqi 在 2026/8/18 10:31, liuqiqi@kylinos.cn 写道: > From: Qiqi Liu > > Extend the memcg charging infrastructure to support per-tier accounting. > After a successful global charge (try_charge_memcg), charge_memcg() > attempts per-tier charging. If the tier charge fails, the global charge > is rolled back via refill_stock() to maintain a consistent state. > > Per-tier limits are enforced via dedicated page_counter objects with > both a hard limit (max) and a soft limit (high): > > - Hard limit: Charging beyond the tier's max triggers reclaim scoped > to that tier's NUMA nodes and retries the charge. If reclaim fails, > OOM is invoked, mirroring memory.max behavior. PF_MEMALLOC > allocations force-charge past the tier max without reclaim (recursion > guard); __GFP_NOFAIL/__GFP_HIGH allocations are force-charged past > the tier max only after reclaim and OOM both fail. > > - Soft limit: The charge always succeeds, but if a tier exceeds its > high watermark, the charge path schedules tier_high_work to perform > asynchronous reclaim. > > The folio lifecycle is updated accordingly: > > - Charging: Attempt per-tier charging after global success; roll back > the global charge on tier failure. > - Uncharging: Directly uncharge the tier counter. > - Replacement: Force-charge the new folio to its tier; the old folio > is uncharged upon freeing. > - Migration: Keep the global usage unchanged; uncharge the old tier > and charge the new tier to reflect the folio's new location. > > This patch implements per-tier accounting for LRU folios (anon and file). > > Signed-off-by: Qiqi Liu > --- > include/linux/memcontrol.h | 1 + > mm/memcontrol.c | 198 ++++++++++++++++++++++++++++++++++++- > 2 files changed, 197 insertions(+), 2 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index c0f5929a87bf..fa944e4bc5ad 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -330,6 +330,7 @@ struct mem_cgroup { > > spinlock_t tier_lock; > struct list_head tier_counters; > + struct work_struct tier_high_work; > > struct mem_cgroup_per_node *nodeinfo[]; > }; > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 70efe01bc36f..30f24604010c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2433,6 +2433,46 @@ static int memcg_tier_counter_create(struct mem_cgroup *memcg, > return 0; > } > > +static void memcg_charge_tier_id(struct mem_cgroup *memcg, int tier_id, > + unsigned long nr_pages) > +{ > + struct memcg_tier_counter *tc; > + > + if (tier_id < 0) > + return; > + rcu_read_lock(); > + tc = memcg_tier_counter_find(memcg, tier_id); > + if (tc) > + page_counter_charge(&tc->counter, nr_pages); > + rcu_read_unlock(); > +} > + > +static void memcg_uncharge_tier_id(struct mem_cgroup *memcg, int tier_id, > + unsigned long nr_pages) > +{ > + struct memcg_tier_counter *tc; > + > + if (tier_id < 0) > + return; > + rcu_read_lock(); > + tc = memcg_tier_counter_find(memcg, tier_id); > + if (tc) > + page_counter_uncharge(&tc->counter, nr_pages); > + rcu_read_unlock(); > +} > + > +static void memcg_charge_tier(struct mem_cgroup *memcg, struct folio *folio, > + unsigned long nr_pages) > +{ > + memcg_charge_tier_id(memcg, node_to_tier_id(folio_nid(folio)), nr_pages); > +} > + > +static void memcg_uncharge_tier(struct mem_cgroup *memcg, struct folio *folio, > + unsigned long nr_pages) > +{ > + memcg_uncharge_tier_id(memcg, node_to_tier_id(folio_nid(folio)), nr_pages); > +} > + > static void memcg_free_tier_counters(struct mem_cgroup *memcg) > { > struct memcg_tier_counter *tc, *tmp; > @@ -2445,6 +2485,49 @@ static void memcg_free_tier_counters(struct mem_cgroup *memcg) > spin_unlock(&memcg->tier_lock); > } > > +static unsigned long > +reclaim_tier(struct mem_cgroup *memcg, unsigned int nr_pages, gfp_t gfp_mask, > + nodemask_t *nmp) > +{ > + unsigned long nr_reclaimed, pflags; > + > + psi_memstall_enter(&pflags); > + nr_reclaimed = try_to_free_mem_cgroup_pages_nodemask(memcg, nr_pages, gfp_mask, > + MEMCG_RECLAIM_MAY_SWAP, NULL, nmp); > + psi_memstall_leave(&pflags); > + return nr_reclaimed; > +} > + > +static void tier_high_work_func(struct work_struct *work) > +{ > + struct mem_cgroup *memcg; > + struct memcg_tier_counter *tc; > + /* Few tiers in practice (2-4); cap is generous. */ > + int over_ids[16]; > + int nr_over = 0; > + int i; > + > + memcg = container_of(work, struct mem_cgroup, tier_high_work); > + > + spin_lock(&memcg->tier_lock); > + list_for_each_entry(tc, &memcg->tier_counters, list) { > + if (page_counter_read(&tc->counter) > READ_ONCE(tc->counter.high)) { > + if (nr_over < ARRAY_SIZE(over_ids)) > + over_ids[nr_over++] = tc->tier_id; > + } > + } > + spin_unlock(&memcg->tier_lock); > + > + for (i = 0; i < nr_over; i++) { > + nodemask_t nodes; > + > + if (tier_id_to_nodemask(over_ids[i], &nodes) || > + nodes_empty(nodes)) > + continue; > + reclaim_tier(memcg, MEMCG_CHARGE_BATCH, GFP_KERNEL, &nodes); > + } > +} > + > /* > * Clamp the maximum sleep time per allocation batch to 2 seconds. This is > * enough to still cause a significant slowdown in most cases, while still > @@ -2873,6 +2956,90 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > return 0; > } > > +static int try_charge_memcg_tier(struct mem_cgroup *memcg, gfp_t gfp_mask, > + unsigned int nr_pages, int tier_id) > +{ > + struct memcg_tier_counter *tc; > + struct page_counter *counter; > + int nr_retries = MAX_RECLAIM_RETRIES; > + unsigned long nr_reclaimed = 0; > + bool passed_oom = false; > + nodemask_t nodes, *nmp = NULL; > + > + if (tier_id < 0) > + return 0; > + > + rcu_read_lock(); > + tc = memcg_tier_counter_find(memcg, tier_id); > + rcu_read_unlock(); > + if (!tc) > + return 0; > + > +retry: > + if (page_counter_try_charge(&tc->counter, nr_pages, &counter)) > + goto success; > + > + /* Over max -> reclaim. */ > + if (unlikely(current->flags & PF_MEMALLOC)) > + goto force; > + if (unlikely(task_in_memcg_oom(current))) > + goto nomem; > + if (!gfpflags_allow_blocking(gfp_mask)) > + goto nomem; > + > + if (!tier_id_to_nodemask(tier_id, &nodes) && !nodes_empty(nodes)) > + nmp = &nodes; > + > + nr_reclaimed = reclaim_tier(memcg, nr_pages, gfp_mask, nmp); > + If the nodemask lookup fails, nmp stays NULL and reclaim scans all nodes - enforcing tier4.max evicts from tier22, and the freed pages are on the wrong tier so it doesn't even help. I'd goto nomem here. Also two nits: struct page_counter *counter is never read; and the function relies on the caller's css reference to keep tc valid across reclaim_tier()/mem_cgroup_oom() (the RCU lock only covers the list walk) - worth a comment before someone adds a new caller. Thanks, Tao > + if (page_counter_read(&tc->counter) + nr_pages <= READ_ONCE(tc->counter.max)) > + goto retry; > + if (gfp_mask & __GFP_NORETRY) > + goto nomem; > + if (nr_reclaimed && nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER)) > + goto retry; > + if (nr_retries--) > + goto retry; > + if (gfp_mask & __GFP_RETRY_MAYFAIL) > + goto nomem; > + if (passed_oom && task_is_dying()) > + goto nomem; > + if (mem_cgroup_oom(memcg, gfp_mask, get_order(nr_pages * PAGE_SIZE))) { > + passed_oom = true; /* tier max is a hard limit: OOM, like memory.max */ > + nr_retries = MAX_RECLAIM_RETRIES; > + goto retry; > + } > + goto nomem; > +success: > + do { > + struct memcg_tier_counter *tc_this; > + > + rcu_read_lock(); > + tc_this = memcg_tier_counter_find(memcg, tier_id); > + if (tc_this && > + page_counter_read(&tc_this->counter) > READ_ONCE(tc_this->counter.high) && > + !work_pending(&memcg->tier_high_work)) { > + schedule_work(&memcg->tier_high_work); > + rcu_read_unlock(); > + break; > + } > + rcu_read_unlock(); > + } while ((memcg = parent_mem_cgroup(memcg))); > + return 0; > +nomem: > + if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH))) > + return -ENOMEM; > + > +force: > + /* > + * Force-charge past the tier max for reclaim/privileged allocations > + * (PF_MEMALLOC, or __GFP_NOFAIL/__GFP_HIGH that fell through from > + * nomem) -- not skip -- so the page is in tier.current too. > + */ > + page_counter_charge(&tc->counter, nr_pages); > + return 0; > +} > + > static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > unsigned int nr_pages) > { > @@ -4216,6 +4383,7 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent) > INIT_WORK(&memcg->high_work, high_work_func); > spin_lock_init(&memcg->tier_lock); > INIT_LIST_HEAD(&memcg->tier_counters); > + INIT_WORK(&memcg->tier_high_work, tier_high_work_func); > vmpressure_init(&memcg->vmpressure); > INIT_LIST_HEAD(&memcg->memory_peaks); > INIT_LIST_HEAD(&memcg->swap_peaks); > @@ -4439,6 +4607,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css) > > vmpressure_cleanup(&memcg->vmpressure); > cancel_work_sync(&memcg->high_work); > + cancel_work_sync(&memcg->tier_high_work); > memcg_free_tier_counters(memcg); > memcg1_remove_from_trees(memcg); > free_shrinker_info(memcg); > @@ -5224,8 +5393,17 @@ static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg, > > objcg = get_obj_cgroup_from_memcg(memcg); > /* Do not account at the root objcg level. */ > - if (!obj_cgroup_is_root(objcg)) > + if (!obj_cgroup_is_root(objcg)) { > ret = try_charge_memcg(memcg, gfp, folio_nr_pages(folio)); > + if (!ret) { > + int tid = node_to_tier_id(folio_nid(folio)); > + > + ret = try_charge_memcg_tier(memcg, gfp, folio_nr_pages(folio), tid); > + /* tier over max / OOM: undo the memory charge */ > + if (ret) > + refill_stock(memcg, folio_nr_pages(folio)); > + } > + } > if (ret) { > obj_cgroup_put(objcg); > return ret; > @@ -5385,8 +5563,11 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug) > ug->nr_kmem += nr_pages; > } else { > /* LRU pages aren't accounted at the root level */ > - if (!obj_cgroup_is_root(objcg)) > + if (!obj_cgroup_is_root(objcg)) { > ug->nr_memory += nr_pages; > + memcg_uncharge_tier(obj_cgroup_memcg(objcg), folio, > + nr_pages); > + } > ug->pgpgout++; > > WARN_ON_ONCE(folio_unqueue_deferred_split(folio)); > @@ -5461,6 +5642,7 @@ void mem_cgroup_replace_folio(struct folio *old, struct folio *new) > page_counter_charge(&memcg->memory, nr_pages); > if (do_memsw_account()) > page_counter_charge(&memcg->memsw, nr_pages); > + memcg_charge_tier(memcg, new, nr_pages); > } > > obj_cgroup_get(objcg); > @@ -5503,6 +5685,18 @@ void mem_cgroup_migrate(struct folio *old, struct folio *new) > if (!objcg) > return; > > + /* Re-account the per-tier breakdown if the folio moved across tiers. */ > + if (!obj_cgroup_is_root(objcg)) { > + struct mem_cgroup *memcg = obj_cgroup_memcg(objcg); > + int old_tier = node_to_tier_id(folio_nid(old)); > + int new_tier = node_to_tier_id(folio_nid(new)); > + > + if (old_tier != new_tier) { > + memcg_uncharge_tier_id(memcg, old_tier, folio_nr_pages(old)); > + memcg_charge_tier_id(memcg, new_tier, folio_nr_pages(new)); > + } > + } > + > /* Transfer the charge and the objcg ref */ > commit_charge(new, objcg); >