Re: Interpreting perf stat on netperf and netserver
From: Jean-Michel Hautbois <hidden>
Date: 2012-01-19 08:29:26
2012/1/18 Rick Jones [off-list ref]:
On 01/18/2012 03:33 AM, Jean-Michel Hautbois wrote:quoted
Hi all, I am currently using netperf/netserver in order to characterize a benet emulex network device on a machine with 2 Xeon5670. I am using the latest linux kernel from git (3.2.0+). I am facing several issues, and I am trying to understand the following perf stat launched on netserver : Performance counter stats for process id '5043':If you aren't already you may want to gather system-wide data as well - not everything networking is guaranteed to run in the netserver's (or netperf's) context. Might also be good to include the netperf command line driving that netserver. That will help folks know if the netserver is receiving data (_STREAM), sending data (_MAERTS) or both (_RR) (though perhaps that can be gleaned from the routine names in the profile.
Well, I am only launching netserver without any parameter.
quoted
15452.992135 task-clock # 0.450 CPUs utilized 189678 context-switches # 0.012 M/sec 5 CPU-migrations # 0.000 M/sec 275 page-faults # 0.000 M/sec 48490467936 cycles # 3.138 GHz 33005879963 stalled-cycles-frontend # 68.07% frontend cycles idle 16325855769 stalled-cycles-backend # 33.67% backend cycles idle 27340520316 instructions # 0.56 insns per cycle # 1.21 stalled cycles per insn 4745604818 branches # 307.099 M/sec 67513124 branch-misses # 1.42% of all branches 34.303567279 seconds time elapsed I am trying to understand the "stalled-cycles-frontend" and "stalled-cycles-backend" lines. It seems that frontend is high, and in red :) but I can't say why...Perhaps the stalls are for cache misses - at least cache misses are a common reason for stalls. I believe that perf has a way to be more specific about the PMU events of interest.
Yes, there is some events for that :). But I didn't know if stall was cache misses related or not :). JM