From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Anthony Liguori <aliguori@us.ibm.com>, Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] Re: [Qemu-commits] [COMMIT 3086844] Instead of writing a zero page, madvise it away
Date: Mon, 22 Jun 2009 20:38:00 +0100 [thread overview]
Message-ID: <200906222038.01469.paul@codesourcery.com> (raw)
In-Reply-To: <4A3FB95D.3060404@us.ibm.com>
> >>> We have the same issue on the migration source node. I don't see a
> >>> simple way to solve it, though.
> >>
> >> I don't follow. In this case, the issue is:
> >>
> >> 1) Start a guest with 1024, balloon down to 128MB. RSS size is now
> >> ~128MB
> >> 2) Live migrate to a different node
> >> 3) RSS on different node jumps to ~1GB
> >
> > 3.5) RSS on source node jumps to ~1GB, since reading the page
> > instantiates the pte
>
> Surely we can do better here...
Huh, I'm surprised we have to. I was expecting linux to populate the region
with CoW mappings of a single zero page, but apparently not. I guess reading a
zero page without writing to it is a fairly rare case, and it's usually better
to instantiate a writable page on the first access.
Paul
next prev parent reply other threads:[~2009-06-22 19:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200906221549.n5MFn3Qd015389@d03av02.boulder.ibm.com>
2009-06-22 16:12 ` [Qemu-devel] Re: [Qemu-commits] [COMMIT 3086844] Instead of writing a zero page, madvise it away Avi Kivity
2009-06-22 16:25 ` Anthony Liguori
2009-06-22 16:38 ` Avi Kivity
2009-06-22 16:58 ` Anthony Liguori
2009-06-22 17:12 ` Avi Kivity
2009-06-22 17:03 ` Anthony Liguori
2009-06-22 17:20 ` Avi Kivity
2009-06-22 17:37 ` Anthony Liguori
2009-06-22 18:01 ` Avi Kivity
2009-06-22 17:44 ` Anthony Liguori
2009-06-22 18:04 ` Avi Kivity
2009-06-22 19:38 ` Paul Brook [this message]
2009-06-22 19:49 ` Anthony Liguori
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