Re: [pagevec] resize pagevec to O(lg(NR_CPUS))

Nick Piggin
2004-09-12T05:28:18Z

William Lee Irwin III wrote:

>
> It's unclear what you're estimating the size of. PAGEVEC_SIZE of 62

Overhead of the loaded pagevec.

[snip]

>
> mapping->tree_lock is affected as well as zone->lru_lock. The workload
> obviously has to touch the relevant locks for pagevecs to be relevant;
> however, the primary factor in the effectiveness of pagevecs is the
> lock transfer time, which is not likely to vary significantly on boxen
> such as the OSDL STP machines. You should use a workload stressing
> mapping->tree_lock via codepaths using radix_tree_gang_lookup() and
> getting runtime on OSDL's NUMA-Q or otherwise asking SGI to test its
> effects, otherwise you're dorking around with boxen with identical
> characteristics as far as batched locking is concerned.
>

Yeah I forgot about that. I guess it probably would be easier to
get contention on the tree lock.