On 01/13/2014 07:41 PM, Josh Boyer wrote: >> We tried, quite a bit, to try and get the xen stuff backported into the >> 2.6.32-EL6 kernel, but given the patch overlap was something we cant >> control and lack the time and technical depth in kernel code to maintain >> that longer term ( this was essentially Johnny and me, doing this over >> and above most other things ), it was just easier to go down that route. I'd be very interested to see a list of commits and corresponding benchmarks for consideration into RHEL. > OK. Those kinds of reasons are what I would expect to drive a > divergence from the disto kernel. I'm curious to see how those kinds > of situations work out in terms of bug reports and additional > maintenance burden. > >> Secondly, there are quite a few anecdotal pieces on dramatic performance >> improvements in newer kernels, I know atleast one of the top 5 CDN's ( >> ie carry > 25Gibt/sec ) that recently switched over from the distro >> centos kernel to a inhouse 3.10 build for 'network perforamnce'. >> >> In quotes, because repeated questions and pokes in various media have >> failed to get a reasonable, tangiable, technical response out of them >> beyond 'network perforamance'. > > Interesting. I suppose it's possible but without actually data > there's really no way to tell. It might even be that they modified > 3.10 themselves to gain that performance and are reluctant to talk > about it? I suppose you don't have any additional details. We did a ton of performance work for RHEL6.5 and are beating upstream performance in various benchmarks while we have a minimal gap in a few benchmarks. Some of them track down to a difference in how memory accounting is performed. That is of course assuming a stock kernel without any bypass technology such as DPDK or SR-IOV. Just bumping to 3.10 or 3.12 is not going to be an universal performance booster fix.