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sched/numa, mm: Revert to checking pmd/pte_write instead of VMA flags 

Commit:

  4d94246699 ("mm: convert p[te|md]_mknonnuma and remaining page table manipulations")

changed NUMA balancing from _PAGE_NUMA to using PROT_NONE, and was quickly
found to introduce a regression with NUMA grouping.

It was followed up by these commits:

 53da3bc2ba ("mm: fix up numa read-only thread grouping logic")
 bea66fbd11 ("mm: numa: group related processes based on VMA flags instead of page table flags")
 b191f9b106 ("mm: numa: preserve PTE write permissions across a NUMA hinting fault")

The first of those two commits try alternate approaches to NUMA
grouping, which apparently do not work as well as looking at the PTE
write permissions.

The latter patch preserves the PTE write permissions across a NUMA
protection fault. However, it forgets to revert the condition for
whether or not to group tasks together back to what it was before
v3.19, even though the information is now preserved in the page tables
once again.

This patch brings the NUMA grouping heuristic back to what it was
before commit 4d94246699, which the changelogs of subsequent
commits suggest worked best.

We have all the information again. We should probably use it.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: aarcange@redhat.com
Cc: linux-mm@kvack.org
Cc: mgorman@suse.de
Link: http://lkml.kernel.org/r/20160908213053.07c992a9@annuminas.surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Rik van Riel 2016-09-08 21:30:53 -04:00 committed by Ingo Molnar
parent b95202a3b6
commit d59dc7bcfa
2 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
mm/huge_memory.c
View File

@ -1168,7 +1168,7 @@ int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
}
/* See similar comment in do_numa_page for explanation */
if (!(vma->vm_flags & VM_WRITE))
if (!pmd_write(pmd))
flags |= TNF_NO_GROUP;
/*

2
mm/memory.c
View File

@ -3398,7 +3398,7 @@ static int do_numa_page(struct fault_env *fe, pte_t pte)
* pte_dirty has unpredictable behaviour between PTE scan updates,
* background writeback, dirty balancing and application behaviour.
*/
if (!(vma->vm_flags & VM_WRITE))
if (!pte_write(pte))
flags |= TNF_NO_GROUP;
/*