linux-kernel - Re: missing madvise functionality

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Date:	Thu, 05 Apr 2007 17:39:53 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Nick Piggin <nickpiggin@...oo.com.au>,
	Ulrich Drepper <drepper@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jakub Jelinek <jakub@...hat.com>,
	Linux Memory Management <linux-mm@...ck.org>
Subject: Re: missing madvise functionality

Andrew Morton wrote:

> #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS

> I wonder which way you're using, and whether using the other way changes
> things.

I'm using the default Fedora config file, which has
NR_CPUS defined to 64 and CONFIG_SPLIT_PTLOCK_CPUS
to 4, so I am using the split locks.

However, I suspect that each 512kB malloced area
will share one page table lock with 4 others, so
some contention is to be expected.

>> For more real world workloads, like the MySQL sysbench one,
>> I still suspect that your patch would improve things.
>>
>> Time to move back to debugging other stuff, though.
>>
>> Andrew, it would be nice if our patches could cook in -mm
>> for a while.  Want me to change anything before submitting?
> 
> umm.  I took a quick squint at a patch from you this morning and it looked
> OK to me.  Please send the finalish thing when it is fully baked and
> performance-tested in the various regions of operation, thanks.

Will do.

Ulrich has a test version of glibc available that
uses MADV_DONTNEED for free(3), that should test
this thing nicely.

I'll run some tests with that when I get the
time, hopefully next week.

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.
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