On 10.04.14 05:28, Liu ping fan wrote:
On Mon, Apr 7, 2014 at 4:36 PM, Alexander Graf <agraf@xxxxxxx> wrote:
On 07.04.14 09:42, Aneesh Kumar K.V wrote:
Alexander Graf <agraf@xxxxxxxx> writes:
On 03.04.14 04:36, Liu ping fan wrote:
Hi Alex, could you help to pick up this patch? since v3.14 kernel can
enable numa fault for powerpc.
What bad happens without this patch? We map a page even though it was
declared to get NUMA migrated? What happens next?
Nothing much, we won't be properly accounting the numa access in the
host. What we want to achieve is to convert a guest access of the page to
a host fault so that we can do proper numa access accounting in the
host. This would enable us to migrate the page to the correct numa
node.
Ok, so no breakages, just less performance. I wouldn't consider it stable
material then :).
Sorry to reply late, since I am half out of office during this period.
I am puzzling about you reply. Without this patch, the guest can
NOT sense the numa changes and ask host to put the pages in right
place. So the pages which is used by guest will be always misplaced.
The numa-fault method is inspired by real requirement to improve
performance, so we should also consider the performance drop of guest.
Right?
The patch will get into Linux, I just consider a non-working new feature
not a regression that warrants us to CC stable@vger :). After all
performance shouldn't be worse than without the numa migration feature,
correct?
Alex
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