+ mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes.patch added to mm-hotfixes-unstable branch
The patch titled Subject: mm/page_alloc: fix NUMA stats update for cpu-less nodes has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Dongjoo Seo dongjoo.linux.dev@gmail.com Subject: mm/page_alloc: fix NUMA stats update for cpu-less nodes Date: Wed, 23 Oct 2024 10:50:37 -0700
In the case of memoryless node, when a process prefers a node with no memory(e.g., because it is running on a CPU local to that node), the kernel treats a nearby node with memory as the preferred node. As a result, such allocations do not increment the numa_foreign counter on the memoryless node, leading to skewed NUMA_HIT, NUMA_MISS, and NUMA_FOREIGN stats for the nearest node.
This patch corrects this issue by: 1. Checking if the zone or preferred zone is CPU-less before updating the NUMA stats. 2. Ensuring NUMA_HIT is only updated if the zone is not CPU-less. 3. Ensuring NUMA_FOREIGN is only updated if the preferred zone is not CPU-less.
Example Before and After Patch: - Before Patch: node0 node1 node2 numa_hit 86333181 114338269 5108 numa_miss 5199455 0 56844591 numa_foreign 32281033 29763013 0 interleave_hit 91 91 0 local_node 86326417 114288458 0 other_node 5206219 49768 56849702
- After Patch: node0 node1 node2 numa_hit 2523058 9225528 0 numa_miss 150213 10226 21495942 numa_foreign 17144215 4501270 0 interleave_hit 91 94 0 local_node 2493918 9208226 0 other_node 179351 27528 21495942
Similarly, in the context of cpuless nodes, this patch ensures that NUMA statistics are accurately updated by adding checks to prevent the miscounting of memory allocations when the involved nodes have no CPUs. This ensures more precise tracking of memory access patterns accross all nodes, regardless of whether they have CPUs or not, improving the overall reliability of NUMA stat. The reason is that page allocation from dev_dax, cpuset, memcg .. comes with preferred allocating zone in cpuless node and its hard to track the zone info for miss information.
Link: https://lkml.kernel.org/r/20241023175037.9125-1-dongjoo.linux.dev@gmail.com Signed-off-by: Dongjoo Seo dongjoo.linux.dev@gmail.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Fan Ni nifan@outlook.com Cc: Dan Williams dan.j.williams@intel.com Cc: Adam Manzanares a.manzanares@samsung.com Cc: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/page_alloc.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes +++ a/mm/page_alloc.c @@ -2858,19 +2858,21 @@ static inline void zone_statistics(struc { #ifdef CONFIG_NUMA enum numa_stat_item local_stat = NUMA_LOCAL; + bool z_is_cpuless = !node_state(zone_to_nid(z), N_CPU); + bool pref_is_cpuless = !node_state(zone_to_nid(preferred_zone), N_CPU);
- /* skip numa counters update if numa stats is disabled */ if (!static_branch_likely(&vm_numa_stat_key)) return;
- if (zone_to_nid(z) != numa_node_id()) + if (zone_to_nid(z) != numa_node_id() || z_is_cpuless) local_stat = NUMA_OTHER;
- if (zone_to_nid(z) == zone_to_nid(preferred_zone)) + if (zone_to_nid(z) == zone_to_nid(preferred_zone) && !z_is_cpuless) __count_numa_events(z, NUMA_HIT, nr_account); else { __count_numa_events(z, NUMA_MISS, nr_account); - __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account); + if (!pref_is_cpuless) + __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account); } __count_numa_events(z, local_stat, nr_account); #endif _
Patches currently in -mm which might be from dongjoo.linux.dev@gmail.com are
mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes.patch
I believe this patch should be dropped. Not only it doesn't really describes an actual problem I believe it is indeed incorrect as explained https://lore.kernel.org/all/ZxoEWBakAv64wfhD@tiehlicka/T/#u
On Wed 23-10-24 13:41:25, Andrew Morton wrote:
From: Dongjoo Seo dongjoo.linux.dev@gmail.com Subject: mm/page_alloc: fix NUMA stats update for cpu-less nodes Date: Wed, 23 Oct 2024 10:50:37 -0700
In the case of memoryless node, when a process prefers a node with no memory(e.g., because it is running on a CPU local to that node), the kernel treats a nearby node with memory as the preferred node. As a result, such allocations do not increment the numa_foreign counter on the memoryless node, leading to skewed NUMA_HIT, NUMA_MISS, and NUMA_FOREIGN stats for the nearest node.
This patch corrects this issue by:
- Checking if the zone or preferred zone is CPU-less before updating the NUMA stats.
- Ensuring NUMA_HIT is only updated if the zone is not CPU-less.
- Ensuring NUMA_FOREIGN is only updated if the preferred zone is not CPU-less.
Example Before and After Patch:
- Before Patch:
node0 node1 node2 numa_hit 86333181 114338269 5108 numa_miss 5199455 0 56844591 numa_foreign 32281033 29763013 0 interleave_hit 91 91 0 local_node 86326417 114288458 0 other_node 5206219 49768 56849702
- After Patch: node0 node1 node2
numa_hit 2523058 9225528 0 numa_miss 150213 10226 21495942 numa_foreign 17144215 4501270 0 interleave_hit 91 94 0 local_node 2493918 9208226 0 other_node 179351 27528 21495942
Similarly, in the context of cpuless nodes, this patch ensures that NUMA statistics are accurately updated by adding checks to prevent the miscounting of memory allocations when the involved nodes have no CPUs. This ensures more precise tracking of memory access patterns accross all nodes, regardless of whether they have CPUs or not, improving the overall reliability of NUMA stat. The reason is that page allocation from dev_dax, cpuset, memcg .. comes with preferred allocating zone in cpuless node and its hard to track the zone info for miss information.
Link: https://lkml.kernel.org/r/20241023175037.9125-1-dongjoo.linux.dev@gmail.com Signed-off-by: Dongjoo Seo dongjoo.linux.dev@gmail.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Fan Ni nifan@outlook.com Cc: Dan Williams dan.j.williams@intel.com Cc: Adam Manzanares a.manzanares@samsung.com Cc: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
mm/page_alloc.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes +++ a/mm/page_alloc.c @@ -2858,19 +2858,21 @@ static inline void zone_statistics(struc { #ifdef CONFIG_NUMA enum numa_stat_item local_stat = NUMA_LOCAL;
- bool z_is_cpuless = !node_state(zone_to_nid(z), N_CPU);
- bool pref_is_cpuless = !node_state(zone_to_nid(preferred_zone), N_CPU);
- /* skip numa counters update if numa stats is disabled */ if (!static_branch_likely(&vm_numa_stat_key)) return;
- if (zone_to_nid(z) != numa_node_id())
- if (zone_to_nid(z) != numa_node_id() || z_is_cpuless) local_stat = NUMA_OTHER;
- if (zone_to_nid(z) == zone_to_nid(preferred_zone))
- if (zone_to_nid(z) == zone_to_nid(preferred_zone) && !z_is_cpuless) __count_numa_events(z, NUMA_HIT, nr_account); else { __count_numa_events(z, NUMA_MISS, nr_account);
__count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
if (!pref_is_cpuless)__count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);#endif _
Patches currently in -mm which might be from dongjoo.linux.dev@gmail.com are
mm-page_alloc-fix-numa-stats-update-for-cpu-less-nodes.patch
linux-stable-mirror@lists.linaro.org
-
Andrew Morton -
Michal Hocko