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memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

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Patch series "Various memory tiering fixes", v3.


This patch (of 3):

last_cpupid is only available when memory tiering is off or the folio is
in toptier node.  Complete the check to read last_cpupid when it is
available.

Before the fix, the default last_cpupid will be used even if memory
tiering mode is turned off at runtime instead of the actual value.  This
can prevent task_numa_fault() from getting right numa fault stats, but
should not cause any crash.  User might see performance changes after the
fix.

Link: https://lkml.kernel.org/r/20240724130115.793641-1-ziy@nvidia.com
Link: https://lkml.kernel.org/r/20240724130115.793641-2-ziy@nvidia.com
Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: David Hildenbrand <david@redhat.com>
Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zi Yan 2024-07-24 09:01:13 -04:00 committed by Andrew Morton
parent d2539ed7ee
commit 3eb2091c65
1 changed files with 2 additions and 1 deletions
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3
mm/huge_memory.c
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@ -1707,7 +1707,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
* For memory tiering mode, cpupid of slow memory page is used
* to record page access time. So use default value.
*/
if (node_is_toptier(nid))
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
node_is_toptier(nid))
last_cpupid = folio_last_cpupid(folio);
target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags);
if (target_nid == NUMA_NO_NODE)