Messages in this thread | | | Date | Wed, 26 May 2004 20:06:23 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [2.4] heavy-load under swap space shortage |
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On Wed, 26 May 2004, Marcelo Tosatti wrote:
> Andrea, Hugh, Jun'ichi, > > I think we can merge this patch.
I guess so. I'm unenthusiastic since I've never worked out whether it's _right_, or just an ad hoc hack that happens to work around more fundamental issues, quite successfully in some workloads.
Andrea seems to have devised it to reduce pagemap_lru_lock contention on bigiron, yet here it's solving a different problem. Which may be a sign that it's a great patch, or a sign that we (I!) don't understand what goes on here well enough.
Please don't count me as against it: I just don't know.
(My involvement was earlier when Jun'ichi reported page_table_lock contention there. We were working together on an entirely different kind of patch addressing that issue, when Andrea suggested he try this vm_anon_lru patch. As I understand it, that solved Jun'ichi's particular problem much more satisfactorily than our own dabblings; but I rather dropped out at that point.)
> Its very safe - default behaviour unchanged.
Yes, but please update the comments to reflect that, they imply vm_anon_lru 0 by default, presumably how it was in Andrea's tree.
The tunability, of course, does unfairly make it look more like a hack than it is; but if we're uncertain, yes, a tunable hack is much better than a wrong decision now.
Hugh
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