Messages in this thread | | | Date | Thu, 08 Nov 2007 15:24:08 -0800 (PST) | Subject | Re: Some interesting observations when trying to optimize vmstat handling | From | David Miller <> |
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From: Christoph Lameter <clameter@sgi.com> Date: Thu, 8 Nov 2007 11:58:58 -0800 (PST)
> The problem with cmpxchg_local here is that the differential has to > be read before we execute the cmpxchg_local. So the cacheline is > acquired first in read mode and then made exclusive on executing the > cmpxchg_local.
I bet this can be defeated by prefetching for a write before the read, but of course this won't help if the read is being used to conditionally avoid the cmpxchg_local but I don't think that's what you're trying to do here.
I've always wanted to add a write prefetch at the beginning of all of the sparc64 atomic operation primitives because of this problem. I just never got around to measuring if it's worthwhile or not. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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