Messages in this thread | | | Date | Mon, 2 Mar 2015 18:37:47 -0800 | Subject | Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing significant performance degradation. | From | Linus Torvalds <> |
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On Mon, Mar 2, 2015 at 6:22 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > There might be some other case where the new "just change the > protection" doesn't do the "oh, but it the protection didn't change, > don't bother flushing". I don't see it.
Hmm. I wonder.. In change_pte_range(), we just unconditionally change the protection bits.
But the old numa code used to do
if (!pte_numa(oldpte)) { ptep_set_numa(mm, addr, pte);
so it would actually avoid the pte update if a numa-prot page was marked numa-prot again.
But are those migrate-page calls really common enough to make these things happen often enough on the same pages for this all to matter?
Odd.
So it would be good if your profiles just show "there's suddenly a *lot* more calls to flush_tlb_page() from XYZ" and the culprit is obvious that way..
Linus
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