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Date: Thu, 19 Jan 2012 09:29:04 +0100 From: Jean-Michel Hautbois <jhautbois@...il.com> To: Rick Jones <rick.jones2@...com> Cc: netdev@...r.kernel.org Subject: Re: Interpreting perf stat on netperf and netserver 2012/1/18 Rick Jones <rick.jones2@...com>: > On 01/18/2012 03:33 AM, Jean-Michel Hautbois wrote: >> >> 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. > >> >> 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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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