From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) (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 3FC3F32B9A9 for ; Tue, 17 Mar 2026 05:07:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773724050; cv=none; b=msTlv+jxu8eMCOouY/NnxXI43CknSEYbcgNQ7OLqSRcS9rnGbi2WtFm0jcOexC4FjgGacCrn5dmCKVcrmWCANNqr85Ze7FwgogR0mDGKrykkfCRY2VS87rFIrMXywIEirPoC7vZQSphltx4QO2dyskah8t4ZrXZJZdQfUuOCfl0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773724050; c=relaxed/simple; bh=ttY9j/UpN4+sijyePIBHa17EDf5VtnfJ+i7huWAIl9k=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=sXxfyvVzg6hzEW/2lZOmmQw5wHzeaziHjKrfcf7EMOC1ucL1pCTlZPjSIOAiSmEWFpZVK9q8bcHJ0ePLiqELUvlVaq1PkAPLX1bE7hD9gyYdtsUFnE7o6y+ipYmpVMZnuZ+5u6WG//2nVfwoHbyXm40izXRyvWEU6aKCoE0xVnE= 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=kq8XzDBT; arc=none smtp.client-ip=95.215.58.178 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="kq8XzDBT" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773724045; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=jvrzqhBOTMeu5FRh46JduvKJCMGJbDc0HHQDFMieGFg=; b=kq8XzDBTIQsxWSNBDIDdDU3wpU2A9uAaKLj7F9RRgUTdEKLh/aUKY096/XXdbF1cfVia0G UuxREMFrxr3Gnv+Z8n/bBMoN3+lBsu+rPARb1wyLivp3zdOxajcPEPmzxts+MYlwKHRhra ybVR7w+A29IdIhXoL6edmwz2nJTjky4= From: "JP Kobryn (Meta)" To: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, ying.huang@linux.alibaba.com Cc: apopple@nvidia.com, axelrasmussen@google.com, byungchul@sk.com, cgroups@vger.kernel.org, david@kernel.org, eperezma@redhat.com, gourry@gourry.net, jasowang@redhat.com, hannes@cmpxchg.org, joshua.hahnjy@gmail.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mst@redhat.com, rppt@kernel.org, muchun.song@linux.dev, zhengqi.arch@bytedance.com, rakie.kim@sk.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, surenb@google.com, virtualization@lists.linux.dev, weixugc@google.com, xuanzhuo@linux.alibaba.com, yuanchu@google.com, ziy@nvidia.com, kernel-team@meta.com Subject: [PATCH v3] mm/mempolicy: track user-defined mempolicy allocations Date: Mon, 16 Mar 2026 22:06:57 -0700 Message-ID: <20260317050657.47494-1-jp.kobryn@linux.dev> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT When investigating pressure on a NUMA node, there is no straightforward way to determine which user-defined policies are driving allocations to it. Add NUMA mempolicy allocation counters as new node stat items. These counters track allocations to nodes and also whether the allocations were intentional or fallbacks. The new stats follow the existing numa hit/miss/foreign style and have the following meanings: hit - for nodemask-based policies, allocation succeeded within nodemask - for other policies, allocation succeeded on intended node - counted on the node of the allocation miss - allocation intended for other node, but happened on this one - counted on other node foreign - allocation intended on this node, but happened on other node - counted on this node The existing numa_* counters cannot be adjusted to fill this role because they are incremented in zone_statistics(), which also covers non-policy allocations such as alloc_pages_node(). The mempolicy context is not applicable at that level since in-kernel callers may make their own node decisions independent of any task policy. Allocations where task mempolicy is NULL are excluded since they do not reflect a user designation and are already accounted for in the existing numa_* stats. Counters are exposed per-node in nodeN/vmstat and globally in /proc/vmstat. They provide the information needed in step 3 of the investigation workflow below: 1) Pressure/OOMs reported while system-wide memory is free. 2) Check /proc/zoneinfo or per-node stats in .../nodeN/vmstat to narrow down node(s) under pressure. 3) Check numa_mpol_{hit,miss,foreign} counters (added by this patch) on node(s) to see what policy is driving allocations there (and whether they are intentional vs fallback). - If active: a user-defined policy is driving allocations to the node. Proceed to step 4. - If inactive: pressure is from allocations without a user-defined policy. Stop and investigate task placement or node capacity instead. 4) Use /proc/*/numa_maps to identify tasks using the policy. Signed-off-by: JP Kobryn (Meta) --- v3: - Moved stats off of memcg - Switched from per-policy to aggregated counters (18 -> 3) - Filter allocations with no user-specified policy v2: https://lore.kernel.org/linux-mm/20260307045520.247998-1-jp.kobryn@linux.dev/ - Replaced single per-policy total counter (PGALLOC_MPOL_*) with hit/miss/foreign triplet per policy - Changed from global node stats to per-memcg per-node tracking v1: https://lore.kernel.org/linux-mm/20260212045109.255391-2-inwardvessel@gmail.com/ include/linux/mmzone.h | 5 ++++ mm/mempolicy.c | 53 +++++++++++++++++++++++++++++++++++++++--- mm/vmstat.c | 5 ++++ 3 files changed, 60 insertions(+), 3 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7bd0134c241c..a9407a3b4c8a 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -323,6 +323,11 @@ enum node_stat_item { PGSCAN_ANON, PGSCAN_FILE, PGREFILL, +#ifdef CONFIG_NUMA + NUMA_MPOL_HIT, + NUMA_MPOL_MISS, + NUMA_MPOL_FOREIGN, +#endif #ifdef CONFIG_HUGETLB_PAGE NR_HUGETLB, #endif diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e5528c35bbb8..c3bacc927a21 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2426,6 +2426,47 @@ static struct page *alloc_pages_preferred_many(gfp_t gfp, unsigned int order, return page; } +/* + * Count a user-defined mempolicy allocation. Stats are tracked per-node. + * The following numa_mpol_{hit/miss/foreign} pattern is used: + * + * hit + * - for nodemask-based policies, allocation succeeded within nodemask + * - for other policies, allocation succeeded on intended node + * - counted on the node of the allocation + * miss + * - allocation intended for other node, but happened on this one + * - counted on other node + * foreign + * - allocation intended for this node, but happened on other node + * - counted on this node + */ +static void mpol_count_numa_alloc(struct mempolicy *pol, int intended_nid, + struct page *page, unsigned int order) +{ + int actual_nid = page_to_nid(page); + long nr_pages = 1L << order; + bool is_hit; + + if (!current->mempolicy) + return; + + if (pol->mode == MPOL_BIND || pol->mode == MPOL_PREFERRED_MANY) + is_hit = node_isset(actual_nid, pol->nodes); + else + is_hit = (actual_nid == intended_nid); + + if (is_hit) { + mod_node_page_state(NODE_DATA(actual_nid), NUMA_MPOL_HIT, nr_pages); + } else { + /* account for miss on the fallback node */ + mod_node_page_state(NODE_DATA(actual_nid), NUMA_MPOL_MISS, nr_pages); + + /* account for foreign on the intended node */ + mod_node_page_state(NODE_DATA(intended_nid), NUMA_MPOL_FOREIGN, nr_pages); + } +} + /** * alloc_pages_mpol - Allocate pages according to NUMA mempolicy. * @gfp: GFP flags. @@ -2444,8 +2485,10 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order, nodemask = policy_nodemask(gfp, pol, ilx, &nid); - if (pol->mode == MPOL_PREFERRED_MANY) - return alloc_pages_preferred_many(gfp, order, nid, nodemask); + if (pol->mode == MPOL_PREFERRED_MANY) { + page = alloc_pages_preferred_many(gfp, order, nid, nodemask); + goto out; + } if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && /* filter "hugepage" allocation, unless from alloc_pages() */ @@ -2471,7 +2514,7 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order, gfp | __GFP_THISNODE | __GFP_NORETRY, order, nid, NULL); if (page || !(gfp & __GFP_DIRECT_RECLAIM)) - return page; + goto out; /* * If hugepage allocations are configured to always * synchronous compact or the vma has been madvised @@ -2494,6 +2537,10 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order, } } +out: + if (page) + mpol_count_numa_alloc(pol, nid, page, order); + return page; } diff --git a/mm/vmstat.c b/mm/vmstat.c index b33097ab9bc8..4a8384441870 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1291,6 +1291,11 @@ const char * const vmstat_text[] = { [I(PGSCAN_ANON)] = "pgscan_anon", [I(PGSCAN_FILE)] = "pgscan_file", [I(PGREFILL)] = "pgrefill", +#ifdef CONFIG_NUMA + [I(NUMA_MPOL_HIT)] = "numa_mpol_hit", + [I(NUMA_MPOL_MISS)] = "numa_mpol_miss", + [I(NUMA_MPOL_FOREIGN)] = "numa_mpol_foreign", +#endif #ifdef CONFIG_HUGETLB_PAGE [I(NR_HUGETLB)] = "nr_hugetlb", #endif -- 2.52.0