Messages in this thread | | | Date | Tue, 8 Apr 2003 06:01:52 -0700 | From | William Lee Irwin III <> | Subject | Re: 2.5.67-mm1 |
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On Tue, Apr 08, 2003 at 04:22:39AM -0700, Andrew Morton wrote: > +remove-nr_reverse_maps.patch > Remove /proc/meminfo:ReverseMaps. It is measurably expensive.
This is fine. The changelog comment doesn't look right though. It says it's inferrable from slabinfo; it's meant to measure the number of reverse mappings performed, or aggregate faulted-in virtualspace on the system, or the number of PTE's pointing at userspace data.
The internal fragmentation within slabs is a separate notion. pte_chains carry more than a single pointer, so the net utilization and internal fragmentation of the things allocated can be computed from nr_reverse_maps/(#pte_chains * NR_PTE), and is very different from the internal fragmentation of slabs (there is no relationship whatsoever).
This stuff has been disturbed on several occasions, and effectively lost whatever meaning it had left after PG_direct anyway, regardless of who changed it to mean what, as the accounting was never adjusted to remove PG_direct reverse mappings (the actions, not any kind of space) from the count due to not being able to identify the notion that would be measured by it. nr_shared_reverse_maps? It's dead, kill it.
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