From: Vlastimil Babka <vbabka@suse.cz>
To: Andrea Arcangeli <aarcange@redhat.com>,
James Hartshorn <jhartshorn@connexity.com>
Cc: "Bridgman, John" <John.Bridgman@amd.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: Can we disable transparent hugepages for lack of a legitimate use case please?
Date: Mon, 14 Sep 2015 14:37:13 +0200 [thread overview]
Message-ID: <55F6BF79.4010801@suse.cz> (raw)
In-Reply-To: <20150910164506.GK10639@redhat.com>
On 09/10/2015 06:45 PM, Andrea Arcangeli wrote:
>> >Mysql (tokudb)
>> >https://dzone.com/articles/why-tokudb-hates-transparent
> This seems a THP issue: unless the alternate malloc allocator starts
> using MADV_NOHUGEPAGE, its memory loss would become extreme with the
> split_huge_page pending changes from Kirill. There's little the kernel
> can do about this, in fact Kirill's latest changes goes in the very
> opposite direction of what's needed to reduce the memory footprint for
> this MADV_DONTNEED 4kb case.
>
> With current code however the best you can do is:
>
> echo 0 >/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none
>
> That will guarantee that khugepaged never increases the memory
> footprint after a MADV_DONTNEED done by the alternate malloc
> allocator. Just that will definitely stop to help with the
> split_huge_page pending changes. You could consider testing that but
> if the split_huge_page pending changes are merged, this tuning shall
> disappear.
I don't think it's that pessimistic after Kirill's patchset?
MADV_DONTNEED should still result in unmaps, which results in
split_huge_pmd. Then the THP is put in a shrinker list and will be fully
split in response to memory pressure, see:
[PATCHv10 34/36] thp: introduce deferred_split_huge_page()
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next prev parent reply other threads:[~2015-09-14 12:37 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 [this message]
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
2015-09-09 22:05 ` Andrea Arcangeli
2015-09-03 19:33 ` Andi Kleen
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