Re: Performance of partial object-based rmap

From: Martin J. Bligh (mbligh@aracnet.com)
Date: Thu Feb 20 2003 - 20:44:17 EST


> The performance delta between 2.5.62-mjb1 and 2.5.62-mjb2 is caused
> by the partial object-based rmap patch (written by Dave McCracken).
> I expect this patch to have an increasing impact on workloads with
> more processes, and it should give a substantial space saving as
> well as a performance increase. Results from 16x NUMA-Q system ...
>
> Profile comparison:
>
> before
> 15525 page_remove_rmap
> 6415 page_add_rmap
>
> after
> 2055 page_add_rmap
> 1983 page_remove_rmap

Did some space consumption comparisons on make -j 256:

before:
        24116 pte_chain objects in slab cache
after:
        716 pte_chain objects in slab cache

The vast majority of anonymous pages (for which we're using the non
object based method) are singletons, and hence use pte_direct ...
hence the massive space reduction.

M.

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