Messages in this thread | | | Date | Wed, 27 Feb 2008 16:51:39 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][PATCH] page reclaim throttle take2 |
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On Tue, 26 Feb 2008 23:19:08 -0800 (PST) David Rientjes <rientjes@google.com> wrote: > My suggestion is merely to make the number of concurrent page reclaim > threads be a function of how many online cpus there are. Threads can > easily be added or removed for cpu hotplug events by callback functions. > > That's different than allowing users to change the number of threads with > yet another sysctl. Unless there are situations that can be presented > where tuning the number of threads is advantageous to reduce lock > contention, for example, and not simply working around other VM problems, > then I see no point for an additional sysctl. > > So my suggestion is to implement this in terms of > CONFIG_NUM_RECLAIM_THREADS_PER_CPU and add callback functions for cpu > hotplug events that add or remove this number of threads. >
Hmm, but kswapd, which is main worker of page reclaiming, is per-node. And reclaim is done based on zone. per-zone/per-node throttling seems to make sense.
I know his environment has 4cpus per node but throttle to 3 was the best number in his measurement. Then it seems num-per-cpu is excessive. (At least, ratio(%) is better.) When zone-reclaiming is improved to be scale well, we'll have to change this throttle.
BTW, could someone try his patch on x86_64/ppc ? I'd like to see how contention is heavy on other machines.
Thanks, -kame
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