On 22.07.2013 19:01, Johannes Weiner wrote:
> Hi Zlatko,
>
> On Mon, Jul 22, 2013 at 06:48:52PM +0200, Zlatko Calusic wrote:
>> On 19.07.2013 22:55, Johannes Weiner wrote:
>>> The way the page allocator interacts with kswapd creates aging
>>> imbalances, where the amount of time a userspace page gets in memory
>>> under reclaim pressure is dependent on which zone, which node the
>>> allocator took the page frame from.
>>>
>>> #1 fixes missed kswapd wakeups on NUMA systems, which lead to some
>>>     nodes falling behind for a full reclaim cycle relative to the other
>>>     nodes in the system
>>>
>>> #3 fixes an interaction where kswapd and a continuous stream of page
>>>     allocations keep the preferred zone of a task between the high and
>>>     low watermark (allocations succeed + kswapd does not go to sleep)
>>>     indefinitely, completely underutilizing the lower zones and
>>>     thrashing on the preferred zone
>>>
>>> These patches are the aging fairness part of the thrash-detection
>>> based file LRU balancing.  Andrea recommended to submit them
>>> separately as they are bugfixes in their own right.
>>>
>>
>> I have the patch applied and under testing. So far, so good. It
>> looks like it could finally fix the bug that I was chasing few
>> months ago (nicely described in your bullet #3). But, few more days
>> of testing will be needed before I can reach a quality verdict.
>
> I should have remembered that you talked about this problem... Thanks
> a lot for testing!
>
> May I ask for the zone layout of your test machine(s)?  I.e. how many
> nodes if NUMA, how big Normal and DMA32 (on Node 0) are.
>

I have been reading about NUMA hw for at least a decade, but I guess 
another one will pass before I actually see one. ;) Find /proc/zoneinfo 
attached.

If your patchset fails my case, then nr_{in,}active_file in Normal zone 
will drop close to zero in a matter of days. If it fixes this particular 
imbalance, and I have faith it will, then those two counters will stay 
in relative balance with nr_{in,}active_anon in the same zone. I also 
applied Konstantin's excellent lru-milestones-timestamps-and-ages, and 
graphing of interesting numbers on top of that, which is why I already 
have faith in your patchset. I can see much better balance between zones 
already. But, let's give it some more time...

-- 
Zlatko