On Fri, 2016-04-15 at 21:02 +0000, Butler, Peter wrote: > (Please keep me CC'd to all comments/responses) > > I've tried a kernel upgrade from 3.4.2 to 4.4.0 and see a marked drop in > networking performance. Nothing was changed on the test systems, other than > the kernel itself (and kernel modules). The identical .config used to build > the 3.4.2 kernel was brought over into the 4.4.0 kernel source tree, and any > configuration differences (e.g. new parameters, etc.) were taken as default > values. > > The testing was performed on the same actual hardware for both kernel > versions (i.e. take the existing 3.4.2 physical setup, simply boot into the > (new) kernel and run the same test). The netperf utility was used for > benchmarking and the testing was always performed on idle systems. > > TCP testing yielded the following results, where the 4.4.0 kernel only got > about 1/2 of the throughput: > > Recv Send Send Utilization > Service Demand > Socket Socket Message Elapsed Send Recv > Send Recv > Size Size Size Time Throughput local remote > local remote > bytes bytes bytes secs. 10^6bits/s % S % S > us/KB us/KB > > 3.4.2 13631488 13631488 8952 30.01 9370.29 10.14 6.50 > 0.709 0.454 > 4.4.0 13631488 13631488 8952 30.02 5314.03 9.14 14.31 > 1.127 1.765 > > SCTP testing yielded the following results, where the 4.4.0 kernel only got > about 1/3 of the throughput: > > Recv Send Send Utilization > Service Demand > Socket Socket Message Elapsed Send Recv > Send Recv > Size Size Size Time Throughput local remote > local remote > bytes bytes bytes secs. 10^6bits/s % S % S > us/KB us/KB > > 3.4.2 13631488 13631488 8952 30.00 2306.22 13.87 13.19 > 3.941 3.747 > 4.4.0 13631488 13631488 8952 30.01 882.74 16.86 19.14 > 12.516 14.210 > > The same tests were performed a multitude of time, and are always consistent > (within a few percent). I've also tried playing with various run-time kernel > parameters (/proc/sys/kernel/net/...) on the 4.4.0 kernel to alleviate the > issue but have had no success at all. > > I'm at a loss as to what could possibly account for such a discrepancy...
Maybe new kernel is faster and you have drops somewhere ? nstat >/dev/null netperf -H ... nstat Would help
