Trond Myklebust <trond.myklebust@xxxxxxxxxx> writes: > On Wed, 2009-05-13 at 15:29 -0400, Jeff Moyer wrote: >> Hi, netdev folks. The summary here is: >> >> A patch added in the 2.6.30 development cycle caused a performance >> regression in my NFS iozone testing. The patch in question is the >> following: >> >> commit 47a14ef1af48c696b214ac168f056ddc79793d0e >> Author: Olga Kornievskaia <aglo@xxxxxxxxxxxxxx> >> Date: Tue Oct 21 14:13:47 2008 -0400 >> >> svcrpc: take advantage of tcp autotuning >> >> which is also quoted below. Using 8 nfsd threads, a single client doing >> 2GB of streaming read I/O goes from 107590 KB/s under 2.6.29 to 65558 >> KB/s under 2.6.30-rc4. I also see more run to run variation under >> 2.6.30-rc4 using the deadline I/O scheduler on the server. That >> variation disappears (as does the performance regression) when reverting >> the above commit. > > It looks to me as if we've got a bug in the svc_tcp_has_wspace() helper > function. I can see no reason why we should stop processing new incoming > RPC requests just because the send buffer happens to be 2/3 full. If we > see that we have space for another reply, then we should just go for it. > OTOH, we do want to ensure that the SOCK_NOSPACE flag remains set, so > that the TCP layer knows that we're congested, and that we'd like it to > increase the send window size, please. > > Could you therefore please see if the following (untested) patch helps? I'm seeing slightly better results with the patch: 71548 75987 71557 87432 83538 But that's still not up to the speeds we saw under 2.6.29. The packet capture for one run can be found here: http://people.redhat.com/jmoyer/trond.pcap.bz2 Cheers, Jeff -- 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
