[PATCH 1/5] Use MADV_DONTNEED for freeing in garbage collector

[Richard Guenther]

On Mon, Oct 10, 2011 at 4:04 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> Shouldn't we prefer still "mapped" pages when allocating?  Thus, keep
>> the freepages list "sorted"?
>
> Possibly. I can look at it in a followup if you want.
> I would prefer to not complicate this patch too much.
>
>>
>> With the new params to call release_pages less, how does this
>> interact with using MADV_DONTNEED?  The only reason to delay
>> MADV_DONTNEED is to avoid splitting huge-pages?  Which would
>> mean that we should rather be better at controlling where we allocate
>> from from the free-list?
>
> I first had a patch that tried to cluster inside the freelist
> with multiple passes (and only free aligned quire clusters first), but it
> ran into various problems, so I chose this simpler approach.
>
> With MADV_DONTNEED the param is not really needed I think,
> I mainly added the param for the benefit of hosts that don't
> have MADV_DONTNEED to let them not suffer from fragmentation too much.
> It would be possible to set the thresholds all to 0 if MADV_DONTNEED
> is available.

So can we move the param patch back as a possible followup?

Thanks,
Richard.

> -Andi
>