[Make-wifi-fast] a bit of profiling on the archer

Jesper Dangaard Brouer brouer at redhat.com
Mon Nov 21 11:24:18 EST 2016

On Sat, 19 Nov 2016 10:30:10 -0800
Dave Taht <dave.taht at gmail.com> wrote:

> Jesper/eric:
> If you have any satisfying network oneliners and stats to monitor via
> perf along the lines of
> http://www.brendangregg.com/perf.html#OneLiners
> it would be helpful longer term.

Good point... I'll think where we can easily publish such oneliners.

> The mips platforms have sprouted more events than it ever had before
> (well, until last year, perf didn't work at all):
> Of these besides the cpu-cycles thing, the only stuff I've looked at
> are various wake_tx_queue related events, and I have a scar involved
> in unaligned_accesses (but we're not doing any, soo)
>   branch-instructions OR branches                    [Hardware event]
>   branch-misses                                      [Hardware event]
>   cpu-cycles OR cycles                               [Hardware event]
>   instructions                                       [Hardware event]

I'm very happy to see this is HW events in this platform! :-)
Guess, I should buy one of these ;-)

This is the Archer? which is what kind of CPU?

>   alignment-faults                                   [Software event]
>   bpf-output                                         [Software event]
>   context-switches OR cs                             [Software event]
>   cpu-clock                                          [Software event]
>   cpu-migrations OR migrations                       [Software event]
>   dummy                                              [Software event]
>   emulation-faults                                   [Software event]
>   major-faults                                       [Software event]
>   minor-faults                                       [Software event]
>   page-faults OR faults                              [Software event]
>   task-clock                                         [Software event]

>   L1-dcache-load-misses                              [Hardware cache event]
>   L1-dcache-loads                                    [Hardware cache event]
>   L1-dcache-store-misses                             [Hardware cache event]
>   L1-dcache-stores                                   [Hardware cache event]

>   L1-icache-load-misses                              [Hardware cache event]
>   L1-icache-loads                                    [Hardware cache event]
>   L1-icache-prefetches                               [Hardware cache event]

The icache HW events are actually quite interesting.  And three of
them, on my Intel Skylake CPU I only have "L1-icache-load-misses".

>   LLC-load-misses                                    [Hardware cache event]
>   LLC-loads                                          [Hardware cache event]
>   LLC-store-misses                                   [Hardware cache event]
>   LLC-stores                                         [Hardware cache event]

LLC = Last Level Cache.

Do you have any info on what the cache layout and sizes of this CPU is?
LLC indicate it might have a L2 cache?

>   branch-load-misses                                 [Hardware cache event]
>   branch-loads                                       [Hardware cache event]
>   iTLB-load-misses                                   [Hardware cache event]
>   iTLB-loads                                         [Hardware cache event]
>   rNNN                                               [Raw hardware event descriptor]
>   cpu/t1=v1[,t2=v2,t3 ...]/modifier                  [Raw hardware event descriptor]
>   mem:<addr>[/len][:access]                          [Hardware breakpoint]
>   ath10k:ath10k_htt_pktlog                           [Tracepoint event]
>   ath10k:ath10k_htt_rx_desc                          [Tracepoint event]

You can use tracepoints if you want to find/analyse very specific
issue, but not so useful for general perf monitoring.

Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

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