Re: [Lsf] [LSF][MM] page allocation & direct reclaim latency

[Ying Han <yinghan@google.com>]

On Tue, Mar 29, 2011 at 12:05 PM, Andrea Arcangeli <aarcange@redhat.com> wrote:
> Hi Rik, Hugh and everyone,
>
> On Tue, Mar 29, 2011 at 11:35:09AM -0400, Rik van Riel wrote:
>> On 03/29/2011 12:36 AM, James Bottomley wrote:
>> > Hi All,
>> >
>> > Since LSF is less than a week away, the programme committee put together
>> > a just in time preliminary agenda for LSF.  As you can see there is
>> > still plenty of empty space, which you can make suggestions
>>
>> There have been a few patches upstream by people for who
>> page allocation latency is a concern.
>>
>> It may be worthwhile to have a short discussion on what
>> we can do to keep page allocation (and direct reclaim?)
>> latencies down to a minimum, reducing the slowdown that
>> direct reclaim introduces on some workloads.
>
> I don't see the patches you refer to, but checking schedule we've a
> slot with Mel&Minchan about "Reclaim, compaction and LRU
> ordering". Compaction only applies to high order allocations and it
> changes nothing to PAGE_SIZE allocations, but it surely has lower
> latency than the older lumpy reclaim logic so overall it should be a
> net improvement compared to what we had before.
>
> Should the latency issues be discussed in that track?
>
> The MM schedule has still a free slot 14-14:30 on Monday, I wonder if
> there's interest on a "NUMA automatic migration and scheduling
> awareness" topic or if it's still too vapourware for a real topic and
> we should keep it for offtrack discussions, and maybe we should
> reserve it for something more tangible with patches already floating
> around. Comments welcome.


In page reclaim, I would like to discuss on the magic "8" *
high_wmark() in balance_pgdat(). I recently found the discussion on
thread "too big min_free_kbytes", where I didn't find where we proved
it is still a problem or not. This might not need reserve time slot,
but something I want to learn more on.

--Ying


>
> Thanks,
> Andrea
>
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