[pve-devel] disabling transparent hugepage by default like kernel 2.6.32 ?

Andreas Steinel a.steinel at gmail.com
Wed Sep 9 16:32:23 CEST 2015


Hi,

In my benchmarks, THP increase the memory transaction speed by 5-10% in the
KVM guest if THP is activated on the host side, not in the VM side. I know
that THP for databases is bad, but we are not using THP in the guest where
the database lives. Can someone provide some benchmarks for that case or
further information? Any suggestions?

On Wed, Sep 9, 2015 at 3:45 PM, Daniel Hunsaker <danhunsaker at gmail.com>
wrote:

> What about setting CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS = N?  As I
> understand it, "not set" means "use the default setting the kernel devs
> think is the most sane for normal use", which in this case would be Y...
>
> On Wed, Sep 9, 2015, 06:58 Alexandre DERUMIER <aderumier at odiso.com> wrote:
>
>> >>I could set it in kernel config, for example:
>> >>
>> >>CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y
>> >>
>> >>would that help?
>>
>> Well, this is like  "echo madvise >
>> /sys/kernel/mm/transparent_hugepage/enabled"
>>
>> But I don't see how to set never.
>>
>> maybe
>>
>> # CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS is not set
>> # CONFIG_TRANSPARENT_HUGEPAGE_MADVISE is not set
>>
>>
>> But I don't known how to unset CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS in the
>> new pve-kernel package makefile ?
>>
>>
>> I have tried to add
>>
>> PVE_CONFIG_OPTS= \
>> ..
>> -d CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS \
>> ..
>>
>> but it don't seem to work, I still have
>> CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=Y in .config
>>
>> Any idea ?
>>
>>
>>
>> ----- Mail original -----
>> De: "dietmar" <dietmar at proxmox.com>
>> À: "aderumier" <aderumier at odiso.com>, "pve-devel" <
>> pve-devel at pve.proxmox.com>
>> Envoyé: Mercredi 9 Septembre 2015 06:33:05
>> Objet: Re: [pve-devel] disabling transparent hugepage by default like
>> kernel 2.6.32 ?
>>
>> > I think it's better to disable it by default.
>> >
>> > echo never > /sys/kernel/mm/transparent_hugepage/enabled.
>> >
>> > (I don't known what is the best way to disable it by default)
>>
>> I could set it in kernel config, for example:
>>
>> CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y
>>
>> would that help?
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>
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