Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad forfile/email/web servers | Date | Mon, 27 Sep 2010 11:01:41 +0900 (JST) |
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Hi
> No doubt this is true. The only real difference is that there are more NUMA > machines running mail/web/file servers now than there might have been in the > past. The default made sense once upon a time. Personally I wouldn't mind > the default changing but my preference would be that distribution packages > installing on NUMA machines would prompt if the default should be changed if it > is likely to be of benefit for that package (e.g. the mail, file and web ones).
At first impression, I thought this is cute idea. But, after while thinking, I've found some weak point. The problem is, too many package need to disable zone_reclaim_mode. zone_reclaim doesn't works fine if an application need large working set rather than local node size. It mean major desktop applications (e.g. OpenOffice.org, Firefox, GIMP) need to disable zone_reclaim. It mean even though basic package installation require zone_reclaim disabling. Then, this mechanism doesn't works practically. Even though the user hope to use the machine for hpc, disable zone_reclaim will be turn on anyway.
Probably, opposite switch (default is zone_reclaim=0, and installation MPI library change to zone_reclaim=1) might works. but I can guess why you don't propose this one.
Hmm....
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