Messages in this thread | | | Date | Wed, 27 Feb 2008 11:18:48 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH] page reclaim throttle take2 |
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David Rientjes wrote: > On Wed, 27 Feb 2008, KOSAKI Motohiro wrote: > >>> I disagree, the config option is indeed static but so is the NUMA topology >>> of the machine. It represents the maximum number of page reclaim threads >>> that should be allowed for that specific topology; a maximum should not >>> need to be redefined with yet another sysctl and should remain independent >>> of various workloads. >> ok. >> >>> However, I would recommend adding the word "MAX" to the config option. >> MAX_PARALLEL_RECLAIM_TASK is good word? >> > > I'd use _THREAD instead of _TASK, but I'd also wait for Balbir's input > because perhaps I missed something in my original analysis that this > config option represents only the maximum number of concurrent reclaim > threads and other heuristics are used in addition to this that determine > the exact number of threads depending on VM strain. >
Things are changing, with memory hot-add remove, CPU hotplug , the topology can change and is no longer static. One can create fake NUMA nodes on the fly using a boot option as well.
Since we're talking of parallel reclaims, I think it's a function of CPUs and Nodes. I'd rather keep it as a sysctl with a good default value based on the topology. If we end up getting it wrong, the system administrator has a choice. That is better than expecting him/her to recompile the kernel and boot that. A sysctl does not create problems either w.r.t changing the number of threads, no hard to solve race-conditions - it is fairly straight forward
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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