Re: [PATCH 1/3] mm: completely disable THP by transparent_hugepage=never

[Cong Wang <amwang@redhat.com>]

于 2011年06月21日 00:50, Andrea Arcangeli 写道:
> On Tue, Jun 21, 2011 at 12:34:28AM +0800, Amerigo Wang wrote:
>> transparent_hugepage=never should mean to disable THP completely,
>> otherwise we don't have a way to disable THP completely.
>> The design is broken.
>
> We want to allow people to boot with transparent_hugepage=never but to
> still allow people to enable it later at runtime. Not sure why you
> find it broken... Your patch is just crippling down the feature with
> no gain. There is absolutely no gain to disallow root to enable THP
> later at runtime with sysfs, root can enable it anyway by writing into
> /dev/mem.


What can I do if I don't want to see THP at all? I mean the same
behavior as when my CPU doesn't have PSE.

With this patch, there is no even /sys/kernel/vm/transparent_hugepage/
exists.

>
> Unless you're root and you enable it, it's completely disabled, so I
> don't see what you mean it's not completely disabled. Not even
> khugepaged is started, try to grep of khugepaged... (that wouldn't be
> the same with ksm where ksm daemon runs even when it's off for no
> gain, but I explicitly solved the locking so khugepaged will go away
> when enabled=never and return when enabled=always).

Without this patch, THP is still initialized (although khugepaged is not started),
that is what I don't want to see when I pass "transparent_hugepage=never",
because "never" for me means THP is totally unseen, even not initialized.

Thanks.