From: Vlastimil Babka <vbabka@suse.cz>
To: Konstantin Khlebnikov <koct9i@gmail.com>,
David Rientjes <rientjes@google.com>
Cc: James Hartshorn <jhartshorn@connexity.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andrea Arcangeli <aarcange@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>
Subject: Re: Can we disable transparent hugepages for lack of a legitimate use case please?
Date: Wed, 2 Sep 2015 11:06:38 +0200 [thread overview]
Message-ID: <55E6BC1E.5080300@suse.cz> (raw)
In-Reply-To: <CALYGNiNQBbV8BOVyBUFYHO8i2Hx15T_Zbb+efKMLH5KR93ZQMw@mail.gmail.com>
On 2.9.2015 10:55, Konstantin Khlebnikov wrote:
> On Wed, Sep 2, 2015 at 1:26 AM, David Rientjes <rientjes@google.com> wrote:
>> On Tue, 25 Aug 2015, Vlastimil Babka wrote:
>>
>>>> THP works very well when system has a lot of free memory.
>>>> Probably default should be weakened to "only if we have tons of free
>>>> memory".
>>>> For example allocate THP pages atomically, only if buddy allocator already
>>>> has huge pages. Also them could be pre-zeroed in background.
>>>
>>> I've been proposing series that try to move more THP allocation activity from
>>> the page faults into khugepaged, but no success yet.
>>>
>>> Maybe we should just start with changing the default of
>>> /sys/kernel/mm/transparent_hugepage/defrag to "madvise".
>>
>> I would need to revert this internally to avoid performance degradation, I
>> believe others would report the same.
>
> What about adding new mode "guess" -- something between always and madvise?
>
> In this mode kernel tries to avoid performance impact for non-madvised vmas and
> allocates 0-order pages if hugepages are not available right now.
> (for example do allocations with GFP_NOWAIT)
That's exactly what happens when
/sys/kernel/mm/transparent_hugepage/defrag is set to "madvise".
> I think we'll get all benefits without losing performance.
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next prev parent reply other threads:[~2015-09-02 9:06 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-24 20:12 Can we disable transparent hugepages for lack of a legitimate use case please? James Hartshorn
2015-08-24 20:20 ` Bridgman, John
2015-08-24 20:46 ` James Hartshorn
2015-08-24 23:20 ` Theodore Ts'o
2015-09-10 16:45 ` Andrea Arcangeli
2015-09-10 17:02 ` Andres Freund
2015-09-14 12:37 ` Vlastimil Babka
2015-08-25 9:25 ` Konstantin Khlebnikov
2015-08-25 9:56 ` Vlastimil Babka
2015-09-01 22:26 ` David Rientjes
2015-09-02 8:55 ` Konstantin Khlebnikov
2015-09-02 9:06 ` Vlastimil Babka [this message]
2015-09-09 22:05 ` Andrea Arcangeli
2015-09-03 19:33 ` Andi Kleen
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