Messages in this thread | | | Date | Fri, 1 Apr 2011 23:34:55 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH 0/3] Unmapped page cache control (v5) |
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* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2011-04-01 22:21:26]:
> > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2011-04-01 16:56:57]: > > > > > Hi > > > > > > > > 1) zone reclaim doesn't work if the system has multiple node and the > > > > > workload is file cache oriented (eg file server, web server, mail server, et al). > > > > > because zone recliam make some much free pages than zone->pages_min and > > > > > then new page cache request consume nearest node memory and then it > > > > > bring next zone reclaim. Then, memory utilization is reduced and > > > > > unnecessary LRU discard is increased dramatically. > > > > > > > > > > SGI folks added CPUSET specific solution in past. (cpuset.memory_spread_page) > > > > > But global recliam still have its issue. zone recliam is HPC workload specific > > > > > feature and HPC folks has no motivation to don't use CPUSET. > > > > > > > > I am afraid you misread the patches and the intent. The intent to > > > > explictly enable control of unmapped pages and has nothing > > > > specifically to do with multiple nodes at this point. The control is > > > > system wide and carefully enabled by the administrator. > > > > > > Hm. OK, I may misread. > > > Can you please explain the reason why de-duplication feature need to selectable and > > > disabled by defaut. "explicity enable" mean this feature want to spot corner case issue?? > > > > Yes, because given a selection of choices (including what you > > mentioned in the review), it would be nice to have > > this selectable. > > It's no good answer. :-/
I am afraid I cannot please you with my answers
> Who need the feature and who shouldn't use it? It this enough valuable for enough large > people? That's my question point. >
You can see the use cases documented, including when running Linux as a guest under other hypervisors, today we have a choice of not using host page cache with cache=none, but nothing the other way round. There are other use cases for embedded folks (in terms of controlling unmapped page cache), please see previous discussions.
-- Three Cheers, Balbir
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