Messages in this thread |  | | Date | Mon, 16 Jun 2008 18:46:10 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH 2/3] relay: Fix race condition which occurs when reading across CPUs. |
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On Mon, Jun 16 2008, Eduard - Gabriel Munteanu wrote: > On Mon, 16 Jun 2008 08:22:49 -0400 > Mathieu Desnoyers <compudj@krystal.dyndns.org> wrote: > > > Hi Eduard, > > Hi. > > > Two objections against this. First, taking a spinlock _is_ slow in SMP > > because it involves synchronized atomic operations. > > In any case, if we use relay in a hot path, we are doing debugging, so > a couple of atomic operations won't be a big problem. Along with > setting affinity, this shouldn't be a problem.
Ehm no, that is a completely false claim. Relay speed does matter, a great deal. We rely heavily on eg blktrace being as ligt weight as possible to capture millions of events in a very short time frame without impacting performance too much. Relay is NOT just for debugging.
So I completely agree with Mathieu here, and I'm not a big fan of the proposed solution.
-- Jens Axboe
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