Messages in this thread | | | Date | Tue, 25 Feb 2003 23:16:02 +0100 | From | Andrea Arcangeli <> | Subject | Re: Minutes from Feb 21 LSE Call |
| |
On Tue, Feb 25, 2003 at 01:12:55PM -0800, Martin J. Bligh wrote: > >> Because you don't set up and tear down the rmap pte-chains for every > >> fault in / delete of any page ... it just works off the vmas. > > > > so basically it uses the rmap that we always had since at least 2.2 for > > everything but anon mappings, right? this is what DaveM did a few years > > back too. This makes lots of sense to me, so at least we avoid the > > duplication of rmap information, even if it won't fix the anonymous page > > overhead, but clearly it's much lower cost for everything but anonymous > > pages. > > Right ... and anonymous chains are about 95% single-reference (at least for > the case I looked at), so they're direct mapped from the struct page with > no chain at all. Cuts out something like 95% of the space overhead of > pte-chains, and 65% of the time (for kernel compile -j256 on 16x system). > However, it's going to be a little more expensive to *use* the mappings, > so we need to measure that carefully.
Sure, it is more expensive to use them, but all we care about is complexity, and they solve the complexity problem just fine, so I definitely prefer it. Cpu utilization during heavy swapping isn't a big deal IMHO
Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |