Re: [PATCH] allocate page caches pages in round robin fasion

[Andi Kleen <ak@muc.de>]

Jesse Barnes <jbarnes@engr.sgi.com> writes:

> On a NUMA machine, page cache pages should be spread out across the system 
> since they're generally global in nature and can eat up whole nodes worth of 
> memory otherwise.  This can end up hurting performance since jobs will have 
> to make off node references for much or all of their non-file data.
>
> The patch works by adding an alloc_page_round_robin routine that simply 
> allocates on successive nodes each time its called, based on the value of a 
> per-cpu variable modulo the number of nodes.  The variable is per-cpu to 
> avoid cacheline contention when many cpus try to do page cache allocations at 

I don't like this approach using a dynamic counter. I think it would
be better to add a new function that takes the vma and uses the offset
into the inode for static interleaving (anonymous memory would still
use the vma offset). This way you would have a good guarantee that the
interleaving stays interleaved even when the system swaps pages in and
out and you're less likely to get anomalies in the page distribution.

-Andi