Messages in this thread | | | Subject | Re: tree rcu: call_rcu scalability problem? | From | Peter Zijlstra <> | Date | Wed, 02 Sep 2009 21:17:44 +0200 |
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On Wed, 2009-09-02 at 14:27 +0200, Nick Piggin wrote:
> It seems like nearly 2/3 of the cost is here: > /* Add the callback to our list. */ > *rdp->nxttail[RCU_NEXT_TAIL] = head; <<< > rdp->nxttail[RCU_NEXT_TAIL] = &head->next; > > In loading the pointer to the next tail pointer. If I'm reading the profile > correctly. Can't see why that should be a probem though... > > ffffffff8107dee0 <__call_rcu>: /* __call_rcu total: 320971 100.000 */ > 697 0.2172 :ffffffff8107dee0: push %r12
> 921 0.2869 :ffffffff8107df57: push %rdx > 151 0.0470 :ffffffff8107df58: popfq > 183507 57.1725 :ffffffff8107df59: mov 0x50(%rbx),%rax > 995 0.3100 :ffffffff8107df5d: mov %rdi,(%rax)
I'd guess at popfq to be the expensive op here.. skid usually causes the attribution to be a few ops down the line.
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