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Re: [Qemu-devel] [PATCH 2/2] migration/postcopy: Explicitly disallow hug
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] migration/postcopy: Explicitly disallow huge pages |
Date: |
Wed, 5 Oct 2016 10:54:31 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
* Daniel P. Berrange (address@hidden) wrote:
> On Thu, Sep 29, 2016 at 08:09:38PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > At the moment postcopy will fail as soon as qemu tries to register
> > userfault on the RAMBlock pages that are backed by hugepages.
> > However, the kernel is going to get userfault support for hugepage
> > at some point, and we've not got the rest of the QEMU code to support
> > it yet, so fail neatly with an error like:
> >
> > Postcopy doesn't support hugetlbfs yet (/objects/mem1)
> >
> > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > ---
> > migration/postcopy-ram.c | 23 +++++++++++++++++++++++
> > 1 file changed, 23 insertions(+)
> >
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index 9b04778..9723593 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -85,6 +85,23 @@ static bool ufd_version_check(int ufd)
> > }
> >
> > /*
> > + * Check for things that postcopy won't support; returns 0 if the block
> > + * is fine.
> > + */
> > +static int check_range(const char *block_name, void *host_addr,
> > + ram_addr_t offset, ram_addr_t length, void *opaque)
> > +{
> > + RAMBlock *rb = qemu_ram_block_by_name(block_name);
> > +
> > + if (qemu_ram_pagesize(rb) > getpagesize()) {
> > + error_report("Postcopy doesn't support hugetlbfs yet (%s)",
> > block_name);
>
> A small nitpick - I'd suggest s/hugetlbfs/large page sizes/ as this error
> will ultimately bubble up to users, and 'large page sizes' is the conceptual
> feature
Interesting, I'd never heard it called 'large' before.
Everytime I just say 'huge page' to someone I then have to explain it's fine
on transparent huge page.
Dave
>
>
> Regards,
> Daniel
> --
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--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- Re: [Qemu-devel] [PATCH 2/2] migration/postcopy: Explicitly disallow huge pages,
Dr. David Alan Gilbert <=