Re: [PATCH] Avoid calling down_read and down_write during startup

From: Benjamin LaHaise
Date: Fri Feb 24 2006 - 09:43:33 EST


On Thu, Feb 23, 2006 at 10:18:18PM -0500, Alan Stern wrote:
> Ben, earlier you expressed concern about the extra overhead due to
> cache-line contention (on SMP) in the down_read() call added to
> blocking_notifier_call_chain. I don't remember which notifier chain in
> particular you were worried about; something to do with networking.
>
> Does this still bother you? I can see a couple of ways around it.

Yes it's a problem. Any read lock is going to act as a memory barrier,
and we need fewer of those in hot paths, not more to slow things down.

-ben
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