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

["Martin J. Bligh" <mbligh@aracnet.com>]

>> Well, either we're:
>> 
>> 1. Falling back and putting all our most recent accesses off-node.
>> 
>> or.
>> 
>> 2. Not falling back and only able to use one node's memory for any one 
>> (single threaded) app.
>> 
>> Either situation is crap, though I'm not sure which turd we picked right
>> now ... I'd have to look at the code again ;-) I thought it was 2, but
>> I might be wrong.
>>  
> 
> I'm looking at this now. We are doing 1 currently.

In theory, yes. In practice, I have a feeling kswapd will keep us above
the level of free memory where we'd fall back to another zone to allocate,
won't it?
 
> There are a couple of issues. The first is that you need to minimise
> regressions for when working set size is bigger than the local node.

Good point ... that is, indeed, a total bitch to fix.

> I have a patch going now that just reclaims use-once file cache before
> going off node. Seems to help a bit for basic things that just push
> pagecache through the system. It definitely reduces remote allocations
> by several orders of magnitude for those cases.

Makes sense, but doesn't the same thing make sense on a global basis?
I don't feel NUMA is anything magical here ...

M.