Re: page table lock patch V15 [0/7]: overview II

From: Andi Kleen <>
Date: 2005-01-14 15:52:18
Andi Kleen <> writes:
> As you can see cmpxchg is slightly faster for the cache hot case,
> but incredibly slow for cache cold (probably because it does something
> nasty on the bus). This is pretty consistent to Intel and AMD CPUs.
> Given that page tables are likely more often cache cold than hot 
> I would use the lazy variant. 

Sorry, my benchmark program actually had a bug (first loop included
page faults). Here are updated numbers. They are somewhat different:

Athlon 64:
readpte hot 25
readpte cold 171
readpte_cmp hot 18
readpte_cmp cold 162

readpte hot 118
readpte cold 443
readpte_cmp hot 22
readpte_cmp cold 224

The difference is much smaller here.  Assuming cache cold cmpxchg8b is
better, at least on the Intel CPUs which have a slow rmb().


To unsubscribe from this list: send the line "unsubscribe linux-ia64" in
the body of a message to
More majordomo info at
Received on Thu Jan 13 23:52:53 2005

This archive was generated by hypermail 2.1.8 : 2005-08-02 09:20:34 EST