Re: [PATCH] alloc_percpu() fails to allocate percpu data
From: Eric Dumazet
Date: Sat Mar 01 2008 - 08:53:47 EST
Andrew Morton a écrit :
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).
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?
Just coming back from hollidays, sorry for the delay.
I can provide a patch so that L1_CACHE_BYTES is not anymore a compile time
constant if you want, but I am not sure it is worth the trouble ? (and this
certainly not 2.6.{24|25} stuff :) )
Current situation :
L1_CACHE_BYTES is known at compile time, and can be quite large (128 bytes),
while cache_line_size() gives the real cache line size selected at boot time
given the hardware capabilities.
If L1_CACHE_BYTES is not anymore a constant, compiler will also uses plain
divides to compute L1_CACHE_ALIGN()
Maybe uses of L1_CACHE_ALIGN() in fastpath would 'force' us to not only
declare a cache_line_size() but also a cache_line_size_{mask|shift}() so that
x86 could use :
#define L1_CACHE_ALIGN(x) ((((x)+cache_line_mask())) >> cache_line_shift())
#define L1_CACHE_BYTES (cache_line_size())
But I am not sure we want to play these games (we must also make sure nothing
in the tree wants a constant L1_CACHE_BYTES and replace by SMP_CACHE_BYTES)
--
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/