Messages in this thread | | | Subject | Re: [RFC 1/3] non-resident page tracking | From | Peter Zijlstra <> | Date | Tue, 09 Aug 2005 21:15:26 +0200 |
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On Tue, 2005-08-09 at 15:25 -0300, Marcelo Tosatti wrote: > Hi Rik, > > Two hopefully useful comments: > > i) ARC and its variants requires additional information about page > replacement (namely whether the page has been reclaimed from the L1 or > L2 lists). > > How costly would it be to add this information to the hash table? > I've been thinking on reserving another word in the cache-line and use that as a bit-array to keep that information; the only problems with that would be atomicy of the {bucket,bit} tuple and very large cachelines where NUM_NR > 32.
> ii) From my reading of the patch, the provided "distance" information is > relative to each hash bucket. I'm unable to understand the distance metric > being useful if measured per-hash-bucket instead of globally?
The assumption is that IFF the hash function has good distribution properties the per bucket distance is a good approximation of (distance >> nonres_shift).
> > PS: Since remember_page() is always called with the zone->lru_lock held, > the preempt_disable/enable pair is unecessary at the moment... still, > might be better to leave it there for safety reasons. >
There being multiple zones; owning zone->lru_lock does not guarantee uniqueness on the remember_page() path as its a global structure.
-- Peter Zijlstra <a.p.zijlstra@chello.nl>
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