Nick Piggin a écrit :
@@ -2604,10 +2604,10 @@ static inline void *__cache_alloc(kmem_c
local_irq_save(save_flags);
objp = ____cache_alloc(cachep, flags);
+ prefetchw(objp);
local_irq_restore(save_flags);
objp = cache_alloc_debugcheck_after(cachep, flags, objp,
__builtin_return_address(0));
- prefetchw(objp);
return objp;
}
I'm not sure why you moved this prefetchw(obj) : This is not related to your
'non-refcounting' part, is it ?
When I added this prefetchw in slab code, I did place it *after* the
local_irq_restore(save_flags); because I was not sure if the
serialization/barrier (popf) would force the cpu (x86/x86_64 in mind) to either :
- finish all the loads (even if they are speculative/hints) (so giving a bad
latency)
- cancel the speculative loads (so prefetchw() *before* the
local_irq_restore() would be useless.
Thank you
Eric
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