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
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