Re: [PATCH] alloc_percpu() fails to allocate percpu data

From: Christoph Lameter
Date: Wed Feb 27 2008 - 16:57:32 EST


On Wed, 27 Feb 2008, Andrew Morton wrote:

> On Wed, 27 Feb 2008 11:59:32 -0800 (PST)
> Christoph Lameter <clameter@xxxxxxx> wrote:
>
> > Any decision made on what to do about this one? Mike or I can
> > repost the per cpu allocator against mm? The fix by Eric could be used
> > in the interim for 2.6.24?
> >
>
> I suppose I'll merge Eric's patch when I've tested it fully (well, as fully
> as I test stuff).

Urgh. You too?

> It'd be nice to get that cache_line_size()/L1_CACHE_BYTES/L1_CACHE_ALIGN()
> mess sorted out. If it's a mess - I _think_ it is?

Well I tried it when slub went first in and it did not go well. The issue
is that x86 detects the cache line size on bootup. Thus cache_line_size().
Most of the other arch have compile time cache line sizes. Thus
L1_CACHE_BYTES. So L1_CACHE_BYTES is the maximum value that
cache_line_size() can take.

What I was attempting to do is to make x86 have one compile time cache
line size L1_CACHE_BYTES. That raised objections because space was wasted.
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