From: Peter Zijlstra <peterz@infradead.org>
To: Nick Piggin <npiggin@suse.de>
Cc: Paul McKenney <paulmck@us.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: tree rcu: call_rcu scalability problem?
Date: Wed, 02 Sep 2009 21:17:44 +0200 [thread overview]
Message-ID: <1251919064.10394.25.camel@laptop> (raw)
In-Reply-To: <20090902122756.GC12251@wotan.suse.de>
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.
next prev parent reply other threads:[~2009-09-02 19:17 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-02 9:48 tree rcu: call_rcu scalability problem? Nick Piggin
2009-09-02 12:27 ` Nick Piggin
2009-09-02 15:19 ` Paul E. McKenney
2009-09-02 16:24 ` Nick Piggin
2009-09-02 16:37 ` Paul E. McKenney
2009-09-02 16:45 ` Nick Piggin
2009-09-02 16:48 ` Paul E. McKenney
2009-09-02 17:50 ` Nick Piggin
2009-09-02 19:17 ` Peter Zijlstra [this message]
2009-09-03 5:14 ` Paul E. McKenney
2009-09-03 7:45 ` Nick Piggin
2009-09-03 9:01 ` Nick Piggin
2009-09-03 13:28 ` Paul E. McKenney
2009-09-03 7:14 ` Nick Piggin
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