linux-kernel - Re: vmalloc performance

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Date:	Fri, 16 Apr 2010 15:10:56 +0100
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Nick Piggin <npiggin@...e.de>
Subject: Re: vmalloc performance

Hi,

On Fri, 2010-04-16 at 01:51 +0900, Minchan Kim wrote:
[snip]
> Thanks for the explanation. It seems to be real issue. 
> 
> I tested to see effect with flush during rb tree search.
> 
> Before I applied your patch, the time is 50300661 us. 
> After your patch, 11569357 us. 
> After my debug patch, 6104875 us.
> 
> I tested it as changing threshold value.
> 
> threshold	time
> 1000		13892809
> 500		9062110
> 200		6714172
> 100		6104875
> 50		6758316
> 
My results show:

threshold        time
100000           139309948
1000             13555878
500              10069801
200              7813667
100              18523172
50               18546256

> And perf shows smp_call_function is very low percentage.
> 
> In my cases, 100 is best. 
> 
Looks like 200 for me.

I think you meant to use the non _minmax version of proc_dointvec too?
Although it doesn't make any difference for this basic test.

The original reporter also has 8 cpu cores I've discovered. In his case
divided by 4 cpus where as mine are divided by 2 cpus, but I think that
makes no real difference in this case.

I'll try and get some further test results ready shortly. Many thanks
for all your efforts in tracking this down,

Steve.


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