Re: [PATCH 0/5] make slab gfp fair

Christoph Lameter
2007-05-17T19:25:15Z

On Thu, 17 May 2007, Peter Zijlstra wrote:

> The proposed patch doesn't change how the kernel functions at this
> point; it just enforces an existing rule better.

Well I'd say it controls the allocation failures. And that only works if
one can consider the system having a single zone.

Lets say the system has two cpusets A and B. A allocs from node 1 and B
allocs from node 2. Two processes one in A and one in B run on the same
processor.

Node 1 gets very low in memory so your patch kicks in and sets up the
global memory emergency situation with the reserve slab.

Now the process in B will either fail although it has plenty of memory on
node 2.

Or it may just clear the emergency slab and then the next critical alloc
of the process in A that is low on memory will fail.