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Re: [Qemu-devel] qemu and transparent huge pages
From: |
Michael Tokarev |
Subject: |
Re: [Qemu-devel] qemu and transparent huge pages |
Date: |
Wed, 15 Aug 2012 18:22:58 +0400 |
User-agent: |
Mozilla/5.0 (X11; Linux i686 on x86_64; rv:10.0.5) Gecko/20120624 Icedove/10.0.5 |
On 15.08.2012 16:51, Avi Kivity wrote:
> On 08/15/2012 03:45 PM, Michael Tokarev wrote:
>>
>> But apparently, THP does not work still, even with 2Mb
>> alignment: when running a guest, AnonHugePages in
>> /proc/meminfo stays at 0 - either in kvm mode or in tcg
>> mode. Any idea why? What else is needed for THP to work?
>
> It does for me:
>
> AnonHugePages: 368640 kB
>
> Note the patch you reference doesn't impact thp, just kvm's ability to
> propagate them to the shadow page table.
>
>>
>> This is quite a frequent question in #kvm IRC channel,
>> and I always suggested using -mem-path for this, but
>> I'm curios why it doesn't work automatically when it
>> probably should?
>>
>
> Please provide extra info, like the setting of
> /sys/kernel/mm/transparent_hugepage/enabled.
That was it - sort of. Default value here is enabled=madvise.
When setting it to always the effect finally started appearing,
so it is actually working.
But can't qemu set MADV_HUGEPAGE flag too, so it works automatically?
Thanks,
/mjt