Messages in this thread | | | Date | Sun, 11 Sep 2016 17:24:02 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH] sched,numa,mm: revert to checking pmd/pte_write instead of VMA flags |
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On Thu, Sep 08, 2016 at 09:30:53PM -0400, Rik van Riel wrote: > Commit 4d9424669946 ("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 changesets: > > 53da3bc2ba9e ("mm: fix up numa read-only thread grouping logic") > bea66fbd11af ("mm: numa: group related processes based on VMA flags instead of page table flags") > b191f9b106ea ("mm: numa: preserve PTE write permissions across a NUMA hinting fault") > > The first of those two changesets 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 > 3.19, 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 changeset 4d9424669946, which the changelogs of subsequent > changesets suggest worked best. > > We have all the information again. We should probably use it. >
Patch looks ok other than the comment above the second hunk being out of date. Out of curiousity, what workload benefitted from this? I saw a mix of marginal results when I ran this on a 2-socket and 4-socket box.
-- Mel Gorman SUSE Labs
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