On 09.01.2013 22:48, Andrew Morton wrote:
On Wed, 09 Jan 2013 22:41:48 +0100
Zlatko Calusic <zlatko.calusic@xxxxxxxx> wrote:
Currently we take a short nap (HZ/10) and wait for congestion to clear
before taking another pass with lower priority in balance_pgdat(). But
we do that only for the highest zone that we encounter is unbalanced
and congested.
This patch changes that to wait on all congested zones in a single
pass in the hope that it will save us some scanning that way. Also we
take a nap as soon as congested zone is encountered and sc.priority <
DEF_PRIORITY - 2 (aka kswapd in trouble).
...
The patch is against the mm tree. Make sure that
mm-avoid-calling-pgdat_balanced-needlessly.patch is applied first (not
yet in the mmotm tree). Tested on half a dozen systems with different
workloads for the last few days, working really well!
But what are the user-observable effcets of this change? Less kernel
CPU consumption, presumably? Did you quantify it?
And I forgot to answer all the questions... :(
Actually, I did record kswapd CPU usage after 5 days of uptime and I
intend to compare it with the new data (after few more days pass). I
expect maybe slightly better results.
But, I think it's obvious from my first reply that my primary goal with
this patch is correctness, not optimization. So, I won't be dissapointed
a little bit if kswapd CPU usage stays the same, so long as the memory
utilization remains this smooth. ;)
--
Zlatko
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