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Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support |
Date: |
Fri, 12 Mar 2010 17:10:54 +0000 |
User-agent: |
KMail/1.12.4 (Linux/2.6.32-trunk-amd64; KDE/4.3.4; x86_64; ; ) |
> > So shouldn't [the name of] the value the kernel provides for recommended
> > alignment be equally implementation agnostic?
>
> Is sys/kernel/mm/transparent_hugepage directory implementation
> agnostic in the first place?
It's about as agnostic as MADV_HUGEPAGE :-)
> If we want to fully take advantage of the feature (i.e. NPT and qemu
> first 2M of guest physical ram where usually kernel resides) userspace
> has to know the alignment size the kernel recommends.
This is KVM specific, so my gut reaction is you should be asking KVM.
> Only thing I'm undecided about is if this should be called
> hpage_pmd_size or just hpage_size. Suppose amd/intel next year adds
> 64k pages too and the kernel decides to use them too if it fails to
> allocate a 2M page. So we escalate the fallback from 2M -> 64k -> 4k,
> and HPAGE_PMD_SIZE becomes 64k. Still qemu has to align on the max
> possible hpage_size provided by transparent hugepage. So with this new
> reasoning I think hpage_size or max_hpage_size would be better sysfs
> name for this. What do you think?
Agreed.
> hpage_size or max_hpage_size?
No particular preference. Or you could have .../page_sizes list all available
sizes, and have qemu take the first one (or last depending on sort order).
Paul
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, (continued)
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/11
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/11
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/11
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/11
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support,
Paul Brook <=
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Andrea Arcangeli, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Jamie Lokier, 2010/03/12
- Re: [Qemu-devel] [PATCH QEMU] transparent hugepage support, Paul Brook, 2010/03/12