Re: [PATCH] lazy freeing of memory through MADV_FREE

Eric Dumazet
2007-04-21T00:48:49Z

Rik van Riel a écrit :
> 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

545 tps versus 610 tps for one thread ? It seems quite bad, no ?

Could you please find an explanation for this ?

> 2 1032 1136 1196 1200
> 4 1070 1128 2014 2024
> 8 1000 1088 1665 2087
> 16 779 1073 1310 1999
>
>

Thank you