Re: [PATCH] lazy freeing of memory through MADV_FREE

Rik van Riel
2007-04-20T23:53:08Z

Andrew Morton wrote:
> On Fri, 20 Apr 2007 17:38:06 -0400
> Rik van Riel <riel@redhat.com> wrote:
>
>> Andrew Morton wrote:
>>
>>> I've also merged Nick's "mm: madvise avoid exclusive mmap_sem".
>>>
>>> - Nick's patch also will help this problem. It could be that your patch
>>> no longer offers a 2x speedup when combined with Nick's patch.
>>>
>>> It could well be that the combination of the two is even better, but it
>>> would be nice to firm that up a bit.
>> I'll test that.
>
> Thanks.

Well, good news.

It turns out that Nick's patch does not improve peak
performance much, but it does prevent the decline when
running with 16 threads on my quad core CPU!

We _definately_ want both patches, there's a huge benefit
in having them both.

Here are the transactions/seconds for each combination:

vanilla new glibc madv_free kernel madv_free + mmap_sem
threads

1 610 609 596 545
2 1032 1136 1196 1200
4 1070 1128 2014 2024
8 1000 1088 1665 2087
16 779 1073 1310 1999

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