lkml.org 
[lkml]   [2016]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH kernel 1/2] mm: add the related functions to build the free page bitmap
On Tue, Apr 19, 2016 at 03:02:09PM +0000, Li, Liang Z wrote:
> > On Tue, 2016-04-19 at 22:34 +0800, Liang Li wrote:
> > > The free page bitmap will be sent to QEMU through virtio interface and
> > > used for live migration optimization.
> > > Drop the cache before building the free page bitmap can get more free
> > > pages. Whether dropping the cache is decided by user.
> > >
> >
> > How do you prevent the guest from using those recently-freed pages for
> > something else, between when you build the bitmap and the live migration
> > completes?
>
> Because the dirty page logging is enabled before building the bitmap, there is no need
> to prevent the guest from using the recently-freed pages ...
>
> Liang

Well one point of telling host that page is free is so that
it can mark it clean even if it was dirty previously.
So I think you must pass the pages to guest under the lock.
This will allow host optimizations such as marking these
pages MADV_DONTNEED or MADV_FREE.
Otherwise it's all too tied up to a specific usecase -
you aren't telling host that a page is free, you are telling it
that a page was free in the past.

--
MST

\
 
 \ /
  Last update: 2016-04-19 18:41    [W:0.102 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site