Re: missing madvise functionality

[Rik van Riel <riel@redhat.com>]

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.

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