Re: [patch 3/8] mm, mempolicy: remove per-process flag

[Christoph Lameter]

On Wed, 4 Dec 2013, David Rientjes wrote:

>
> Right, but it turns out not to matter in practice.  As one of the non-
> default CONFIG_SLAB users, and PF_MEMPOLICY only does something for
> CONFIG_SLAB, this patch tested to not show any degradation for specjbb
> which stresses the allocator in terms of throughput:
>
> 	   with patch: 128761.54 SPECjbb2005 bops
> 	without patch: 127576.65 SPECjbb2005 bops

Specjbb? What does Java have to do with this?
Can you run the synthetic in kernel slab benchmark.

Like this one https://lkml.org/lkml/2009/10/13/459

> These per-process flags are a scarce resource so I don't think
> PF_MEMPOLICY warrants a bit when it's not shown to be advantageous in
> configurations without mempolicy usage where it's intended to optimize,
> especially for a non-default slab allocator.

PF_MEMPOLICY was advantageous when Paul Jackson introduced and benchmarked
it.

SLUB supports mempolicies through allocate_pages but it will allocate all
objects out of one slab pages before retrieving another page following the
policy. Thats why PF_MEMPOLICY and the other per object handling can be
avoided in its fastpath. Thus PF_MEMPOLICY is not that important there.

However, SLAB is still the allocator in use for RHEL which puts some
importance on still supporting SLAB.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/