Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur
[Posted March 25, 2015 by corbet]
| From: |
| Linus Torvalds <torvalds-AT-linux-foundation.org> |
| To: |
| Mel Gorman <mgorman-AT-suse.de> |
| Subject: |
| Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur |
| Date: |
| Thu, 19 Mar 2015 11:09:15 -0700 |
| Message-ID: |
| <CA+55aFwTcw2rTjPM_EOjPeKNWwdfNVazx+O=YAFXPWw1h==Tgw@mail.gmail.com> |
| Cc: |
| Dave Chinner <david-AT-fromorbit.com>, Ingo Molnar <mingo-AT-kernel.org>, Andrew Morton <akpm-AT-linux-foundation.org>, Aneesh Kumar <aneesh.kumar-AT-linux.vnet.ibm.com>, Linux Kernel Mailing List <linux-kernel-AT-vger.kernel.org>, Linux-MM <linux-mm-AT-kvack.org>, xfs-AT-oss.sgi.com, ppc-dev <linuxppc-dev-AT-lists.ozlabs.org> |
| Archive‑link: | |
Article |
On Thu, Mar 19, 2015 at 7:10 AM, Mel Gorman <mgorman@suse.de> wrote:
> - if (!pmd_dirty(pmd))
> + /* See similar comment in do_numa_page for explanation */
> + if (!(vma->vm_flags & VM_WRITE))
Yeah, that would certainly be a whole lot more obvious than all the
"if this particular pte/pmd looks like X" tests.
So that, together with scanning rate improvements (this *does* seem to
be somewhat chaotic, so it's quite possible that the current scanning
rate thing is just fairly unstable) is likely the right thing. I'd
just like to _understand_ why that write/dirty bit makes such a
difference. I thought I understood what was going on, and was happy,
and then Dave come with his crazy numbers.
Damn you Dave, and damn your numbers and "facts" and stuff. Sometimes
I much prefer ignorant bliss.
Linus
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