From: Andrew Morton <akpm@linux-foundation.org>
To: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mel Gorman <mel@csn.ul.ie>, Johannes Weiner <hannes@cmpxchg.org>,
KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
hughd@google.com,
Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Subject: Re: [PATCH -mm 1/2] mm: fix quadratic behaviour in get_unmapped_area_topdown
Date: Thu, 23 Feb 2012 13:50:07 -0800 [thread overview]
Message-ID: <20120223135007.a4dceeb2.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120223145636.616bef1c@cuia.bos.redhat.com>
On Thu, 23 Feb 2012 14:56:36 -0500
Rik van Riel <riel@redhat.com> wrote:
> When we look for a VMA smaller than the cached_hole_size, we set the
> starting search address to mm->mmap_base, to try and find our hole.
>
> However, even in the case where we fall through and found nothing at
> the mm->free_area_cache, we still reset the search address to mm->mmap_base.
> This bug results in quadratic behaviour, with observed mmap times of 0.4
> seconds for processes that have very fragmented memory.
>
> If there is no hole small enough for us to fit the VMA, and we have
> no good spot for us right at mm->free_area_cache, we are much better
> off continuing the search down from mm->free_area_cache, instead of
> all the way from the top.
This has been at least partially addressed in recent patches from Xiao
Guangrong. Please review his five-patch series starting with "[PATCH
1/5] hugetlbfs: fix hugetlb_get_unmapped_area".
I've already merged those patches and we need to work out what way to
go.
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next prev parent reply other threads:[~2012-02-23 21:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-23 19:54 [PATCH -mm 0/2] speed up arch_get_unmapped_area Rik van Riel
2012-02-23 19:56 ` [PATCH -mm 1/2] mm: fix quadratic behaviour in get_unmapped_area_topdown Rik van Riel
2012-02-23 21:50 ` Andrew Morton [this message]
2012-02-23 21:57 ` Johannes Weiner
2012-02-23 20:00 ` [PATCH -mm 2/2] mm: do not reset mm->free_area_cache on every single munmap Rik van Riel
2012-02-23 21:56 ` Andrew Morton
2012-02-27 16:12 ` Rik van Riel
2012-03-20 18:32 ` Rik van Riel
2012-03-20 19:00 ` Andrea Arcangeli
2012-03-20 19:06 ` Rik van Riel
2012-02-23 21:57 ` Andi Kleen
2012-02-27 16:13 ` Rik van Riel
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