From: Rik van Riel <riel@surriel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org, akpm@linux-foundation.org,
aarcange@redhat.com, minchan@gmail.com,
kosaki.motohiro@gmail.com, andi@firstfloor.org,
hannes@cmpxchg.org, mel@csn.ul.ie, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm v2 01/11] mm: track free size between VMAs in VMA rbtree
Date: Fri, 22 Jun 2012 11:41:33 -0400 [thread overview]
Message-ID: <4FE4922D.8070501@surriel.com> (raw)
In-Reply-To: <1340375872.18025.77.camel@twins>
On 06/22/2012 10:37 AM, Peter Zijlstra wrote:
> On Fri, 2012-06-22 at 10:25 -0400, Rik van Riel wrote:
>> On 06/22/2012 10:13 AM, Peter Zijlstra wrote:
>>> On Fri, 2012-06-22 at 10:11 -0400, Rik van Riel wrote:
>>>>
>>>> I am still trying to wrap my brain around your alternative
>>>> search algorithm, not sure if/how it can be combined with
>>>> arbitrary address limits and alignment...
>>>
>>> for alignment we can do: len += align - 1;
>>
>> We could, but that might lead us to returning -ENOMEM
>> when we actually have memory available.
>>
>> When you consider architectures like HPPA, which use
>> a pretty large alignment, but align everything the same,
>> chances are pretty much every freed hole will have the
>> right alignment...
>
> Well, if you don't your gap heap is next to useless and you'll revert to
> simply walking all gaps until you find a suitable one.
I could see how that might potentially be a problem,
especially when we have a small allocation with large
alignment constraints, eg. HPPA cache alignment.
> I really worry about this search function of yours, its complexity is
> very non obvious.
Let me try implementing your algorithm with arbitrary
address constraints and alignment/colouring.
Basically, we need to remember if the allocation failed
due to bad alignment. If it did, we add shm_align_mask
to the allocation length, and try a second search.
This should result in at worst two whole tree traversals
and one partial traversal. Less on sane architectures,
or for non-MAP_SHARED allocations.
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next prev parent reply other threads:[~2012-06-22 15:41 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-21 21:57 [PATCH -mm v2 00/11] mm: scalable and unified arch_get_unmapped_area Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 01/11] mm: track free size between VMAs in VMA rbtree Rik van Riel
2012-06-22 9:57 ` Peter Zijlstra
2012-06-22 9:58 ` Peter Zijlstra
2012-06-22 14:11 ` Rik van Riel
2012-06-22 14:13 ` Peter Zijlstra
2012-06-22 14:25 ` Rik van Riel
2012-06-22 14:37 ` Peter Zijlstra
2012-06-22 15:41 ` Rik van Riel [this message]
2012-06-25 19:29 ` Peter Zijlstra
2012-06-25 21:52 ` Rik van Riel
2012-06-26 8:31 ` Peter Zijlstra
2012-06-26 13:05 ` Rik van Riel
2012-06-26 13:45 ` Peter Zijlstra
2012-06-26 15:49 ` Rik van Riel
2012-06-27 12:27 ` Peter Zijlstra
2012-06-26 8:37 ` Peter Zijlstra
2012-06-22 10:02 ` Peter Zijlstra
2012-06-29 23:46 ` Michel Lespinasse
2012-07-03 21:37 ` Rik van Riel
2012-07-03 23:16 ` Michel Lespinasse
2012-07-04 10:12 ` Peter Zijlstra
2012-06-21 21:57 ` [PATCH -mm v2 02/11] mm: rearrange vm_area_struct for fewer cache misses Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 03/11] mm: vma_adjust: only call adjust_free_gap when needed Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 04/11] rbtree: add helpers to find nearest uncle node Rik van Riel
2012-06-22 9:49 ` Peter Zijlstra
2012-06-21 21:57 ` [PATCH -mm v2 05/11] mm: get unmapped area from VMA tree Rik van Riel
2012-06-30 1:33 ` Michel Lespinasse
2012-07-03 0:23 ` Michel Lespinasse
2012-06-30 2:42 ` Michel Lespinasse
2012-06-21 21:57 ` [PATCH -mm v2 06/11] mm: arbitrary address ranges for arch_get_unmapped_area Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 07/11] mm: make cache alignment code generic Rik van Riel
2012-06-30 2:22 ` Michel Lespinasse
2012-06-21 21:57 ` [PATCH -mm v2 08/11] mm: remove x86 arch_get_unmapped_area(_topdown) Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 09/11] mm: remove MIPS arch_get_unmapped_area code Rik van Riel
2012-06-21 21:57 ` [PATCH -mm v2 10/11] mm: remove ARM arch_get_unmapped_area functions Rik van Riel
2012-06-22 22:27 ` Russell King - ARM Linux
2012-06-23 17:50 ` Johannes Weiner
2012-06-21 21:57 ` [PATCH -mm v2 11/11] mm: remove SH " Rik van Riel
2012-06-25 2:11 ` Paul Mundt
2012-06-22 14:24 ` [PATCH -mm v2 00/11] mm: scalable and unified arch_get_unmapped_area John Stoffel
2012-06-22 21:47 ` Andrew Morton
2012-06-23 16:03 ` John Stoffel
2012-06-22 15:01 ` Johannes Weiner
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