Re: [PATCH] x86: eliminate redundant/contradicting cache line size config options

Jan Beulich
2009-11-19T08:38:12Z

>>> Nick Piggin <npiggin@suse.de> 19.11.09 09:13 >>>
>On Wed, Nov 18, 2009 at 08:52:40PM -0800, Arjan van de Ven wrote:
>Basically what I think we should do is consider L1_CACHE_BYTES to be
>*the* correct default value to use for 1) avoiding false sharing (which
>seems to be the most common use), and 2) optimal and repeatable per-object
>packing into cachelines (which is more of a micro-optimization to be
>applied carefully to really critical structures).

But then this really shouldn't be called L1_CACHE_... Though I realize
that the naming seems to already be broken - looking over the cache
line specifiers for CPUID leaf 2, there's really no L1 with 128 byte lines,
just two L2s.

One question however is whether e.g. cache line ping-pong between
L3s is really costing that much on non-NUMA, as opposed to it
happening between L1s.

Jan