On Wed, 2009-05-13 at 14:25 -0400, Jim Rees wrote: > Andrew Morton wrote: > > Jeff's computer got slower. Can we fix that? > > TCP autotuning can reduce performance by up to about 10% in some cases. > Jeff found one of these cases. While the autotuning penalty never exceeds > 10% as far as I know, I can provide examples of other cases where autotuning > improves nfsd performance by more than a factor of 100. > > The right thing is to fix autotuning. If autotuning is considered too > broken to use, it should be turned off everywhere, not just in nfsd, as it > hurts/benefits all TCP clients, not just nfs. > > This topic has been discussed before on netdev: > http://www.spinics.net/lists/netdev/msg68650.html > http://www.spinics.net/lists/netdev/msg68155.html Yes, but one consequence of this patch is that the socket send buffer size sk->sk_sndbuf is now initialised to a smaller value than before. This again means that the test for xprt->xpt_ops->xpo_has_wspace() in svc_xprt_enqueue() will fail more often, and so you will be able to process fewer incoming requests in parallel while you are waiting for the send window size to build up. Perhaps the right thing to do here is to allow some limited violation of the xpo_has_wspace() test while the send window is in the process of building up? Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
