Pekka J Enberg wrote:
On Tue, 21 Mar 2006, Andrew Morton wrote:
I've always felt that this was an odd design. Because
a) All that cache-warmth which we get from the constructor's zeroing can
be lost by the time we get around to using an individual object and
b) The object may be cache-cold by the time we free it, and we'll take
cache misses just putting it back into a constructed state for
kmem_cache_free(). And we'll lose that cache warmth by the time we use
this object again.
So from that POV I think (in my simple way) that this is a good patch. But
IIRC, Manfred has reasons why it might not be?
I assume the design comes from Bonwick's paper which states that the
purpose of object constructor is to support one-time initialization of
objects which we're _not_ doing in this case.
I agree - memset just before use is the Right Thing (tm).
One minor point: There are two cache_alloc entry points: __cache_alloc,
which is a forced inline function, and kmem_cache_alloc, which is just a
wrapper for __cache_alloc. Is it really necessary to call __cache_alloc?
The idea is that __cache_alloc is used just by the two high-performance
paths: kmem_cache_alloc and kmalloc. Noone else should use __cache_alloc
directly.
--
Manfred
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