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Date: Mon, 07 May 2007 16:09:11 -0700 (PDT) From: David Miller <davem@...emloft.net> To: bcrl@...ck.org Cc: netdev@...r.kernel.org Subject: Re: [PATCH] fib_info_hashfn leads to long hash chains From: Benjamin LaHaise <bcrl@...ck.org> Date: Sun, 29 Apr 2007 11:03:36 -0400 > Hello > > The patch below fixes a case where fib_find_info() is consume excessive > amounts of CPU during the creation of 10000 PPP interfaces. In access > servers, each point to point link has the same local address, but a different > destination and interface. Because the device is not included in the hash > calculation, the chain grows excessively large and we end up spinning the > CPU walking the list. As near as I can tell, this shouldn't have any negative > sideeffects, but someone with a better understanding of fib_semantics.c will > need to check over it. Cheers, fib_create_info() makes sure that fi->fib_nhs is always at least one. So the conditional can be removed. After a fib_info is create, it's fi->fib_nhs is immutable, it doesn't change. In fact there are some checks for fi->fib_nhs == 0 elsewhere in this code, those are bogus too, and I imagine you saw those when coding up this patch. :-) - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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