Re: The sixty second pmc howto


Robert Watson writes:

(2) Run "pmcstat -S instructions -O /tmp/sample.out" to start sampling of
instruction retirement events, saving the results to /tmp/sample.out.

Dumb question, but what does "instructions" really mean? The number
of instructions, the time spent executing them, ?

<.....>

Since there is no call graph information in the sample, the first few pages of
gprof output will be of limited utility, but the summary table by function is
the bit I found most useful:

You can use gprof -l to suppress the printing of the call-graph profile

My only problem with hwpmc is that it will not work for kernel
modules. I wonder if somebody with enough toolchain fu could take
kldstat output and produce a pre-linked elf executable image
containing kernel+modules which could be used for hwpmc, and also for
crash dump analysis. Or is there another, better, way to get a
complete symbol table of the kernel & all kernel modules?

So if you're doing kernel performance work, and not already using pmc, you
probably should be.

Very much agreed.

Drew
_______________________________________________
freebsd-current@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-current
To unsubscribe, send any mail to "freebsd-current-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: how do threads work?
    ... >> A process cannot consider to switch task unless the flow of instructions ... >> kernel for a little help, in the form of regular timer signals. ... If you now ask, how does the kernel deliver signals, then we are no longer ...
    (comp.os.linux.development.system)
  • Re: Direct Linux syscalls
    ... > int 80h still exist. ... the "sysenter" has better performance because it's a CPU ... One of the slowest instructions turns out to be "int" (especially when also ... changing from the "user stack" to the "kernel stack" and so on and so forth ...
    (comp.os.linux.development.apps)
  • Re: POWER6 on zSeries?
    ... there was some mvs kernel performance assist microcode done for 3033 ... ... 370 instructions already running at or close to hardware speed. ... vm ran the virtual machine in problem mode and all ...
    (bit.listserv.ibm-main)
  • Re: how do threads work?
    ... A process cannot consider to switch task unless the flow of instructions ... kernel for a little help, in the form of regular timer signals. ... Signals do force an interruption of the flow of instructions. ...
    (comp.os.linux.development.system)
  • 2.6.24 panics initializing ne2k in mips.
    ... The 2.6.23 kernel built for mips with the attached .config works fine for me ... Synthesized clear page handler (13 instructions). ... # Other IDE chipsets support ...
    (Linux-Kernel)