Re: missing madvise functionality

Rik van Riel
2007-04-05T15:47:39Z

Andrew Morton wrote:
> On Thu, 05 Apr 2007 03:39:29 -0400 Rik van Riel <riel@redhat.com> wrote:
>
>> Rik van Riel wrote:
>>
>>> MADV_DONTNEED, unpatched, 1000 loops
>>>
>>> real 0m13.672s
>>> user 0m1.217s
>>> sys 0m45.712s
>>>
>>>
>>> MADV_DONTNEED, with patch, 1000 loops
>>>
>>> real 0m4.169s
>>> user 0m2.033s
>>> sys 0m3.224s
>> I just noticed something fun with these numbers.
>>
>> Without the patch, the system (a quad core CPU) is 10% idle.
>>
>> With the patch, it is 66% idle - presumably I need Nick's
>> mmap_sem patch.
>>
>> However, despite being 66% idle, the test still runs over
>> 3 times as fast!
>
> Please quote the context switch rate when testing this stuff (I use vmstat 1).
> I've seen it vary by a factor of 10,000 depending upon what's happening.

About context switches 14000 per second.

I'll go compile in Nick's patch to see if that makes
things go faster. I expect it will.

procs -----------memory---------- ---swap-- -----io---- --system--
-----cpu------
r b swpd free buff cache si so bi bo in cs us sy
id wa st
1 0 0 965232 250024 370848 0 0 0 0 1026 13914 13
21 67 0 0
1 0 0 965232 250024 370848 0 0 0 0 1018 14654 12
20 68 0 0
1 0 0 965232 250024 370848 0 0 0 0 1023 14006 12
21 67 0 0

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