Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

[Hush Bensen]

ä 2013/7/24 19:18, Zlatko Calusic åé:
> On 22.07.2013 18:48, 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.
>
> Well, only 2 days later it's already obvious that the patch is 
> perfect! :)
>
> In the attached image, in the left column are the graphs covering last 
> day and a half. It can be observed that zones are really balanced, and 
> that aging is practically perfect. Graphs on the right column cover 
> last 10 day period, and the left side of the upper graph shows how it 
> would look with the stock kernel after about 20 day uptime (although 
> only a few days is enough to reach such imbalance). File pages in the 
> Normal zone are extinct species (red) and the zone is choke full of 
> anon pages (blue). Having seen a lot of this graphs, I'm certain that 
> it won't happen anymore with your patch applied. The balance is 
> restored! Thank you for your work. Feel free to add:
>
> Tested-by: Zlatko Calusic <zcalusic@xxxxxxxxxxx>

Thanks for your testing Zlatko, could you tell me which benchmark or 
workload you are using? Btw, which tool is used to draw these nice 
pictures? ;-)

> Regards,

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