Messages in this thread | | | Date | Wed, 31 Jul 2013 11:33:39 +0200 | From | Zlatko Calusic <> | Subject | Re: [patch 0/3] mm: improve page aging fairness between zones/nodes |
| |
On 24.07.2013 13:18, Zlatko Calusic wrote: > 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! :) >
Additionaly, on the patched kernel, kswapd burns 30% less CPU cycles. Nice to see that restored balance also eases kswapd's job, but that was to be expected. Measured on the real workload, twice, to be sure.
Regards, -- Zlatko
| |