Re: [PATCH 3/3] perf tools: Add evlist/evlist-verbose control commands

[Jiri Olsa]

On Tue, Dec 15, 2020 at 12:23:43PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Dec 10, 2020 at 09:43:30PM +0100, Jiri Olsa escreveu:
> > Adding new control events to display all evlist events.
> > 
> > The interface string for control file is 'evlist' and
> > 'evlist-verbose'.
> 
> Can't we pass args to such commands?
> 
> Then its just one event, i.e. "evlist", and -v can be passed to it.

it's possible but it adds another processing to the single record thread
where we want to be fast

but I agree it could be helpful to get the other output that evsel__fprintf
can print, and we already call evsel__fprintf, so it's just a matter of
setting 'struct perf_attr_details' properly

I need to check, but perhaps we could use ' ' instead of '-' and have:

  echo 'evlist -v' > control
  echo 'evlist -g' > control
  echo 'evlist -F' > control

and have:

  echo 'enable cycles' > control

instead of:

  echo 'enable-cycles' > control

I'd like to avoid any elaborate parsing logic..

how about that?

> 
> i.e.:
> 
> The commands would be:
> 
> evlist
> 
> That produces:
> 
>  
>    terminal 2:
>      # echo evlist > control
>  
>    terminal 1:
>      # perf record --control=fifo:control,ack -e 'sched:*'
>      ...
>      sched:sched_kthread_stop
>      sched:sched_kthread_stop_ret
>      sched:sched_waking
> 
> And 'evlist -v', that produces:
> 
>    terminal 2:
>      # echo "evlist -v" > control
>  
>    terminal 1:
>      ...
>      sched:sched_kthread_stop: type: 2, size: 120, config: 0x145,      \
>      { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU   \
>      |PERIOD|RAW|IDENTIFIER, read_format: ID, disabled: 1, inherit:    \
>      1, sample_id_all: 1, exclude_guest: 1
>      sched:sched_kthread_stop_ret: type: 2, size: 120, config: 0x144   \
>      , { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU \
>      |PERIOD|RAW|IDENTIFIER, read_format: ID, disabled: 1, inherit: 1, \
>      sample_id_all: 1, exclude_guest: 1
>      ...
> 
> I think we could even change things such that we pass a file descriptor
> for cmd_evlist to use, passing the argv received from the control file,
> etc.

hum, so perf evlist opens/reads perf.data, which we do not have ready
at that point in perf record

> 
> With this in place we could reuse more stuff and allow using this
> control file to obtain information such as 'perf report --header-only',
> etc.
> 
> echo "report --header-only" > control would get us the same thing as
> 'perf report --header-only' for an existing perf.data file:

all those header data are written when record is exiting or dumped
for switch output, so we don't have that data at that moment control
command is received

> 
> 
> # perf report --header-only
> # ========
> # captured on    : Tue Dec 15 12:21:23 2020
> # header version : 1
> # data offset    : 432
> # data size      : 1648
> # feat offset    : 2080
> # hostname : five
> # os release : 5.10.0-rc7+
> # perf version : 5.10.rc6.gc56d2601b5d0
> # arch : x86_64
> # nrcpus online : 24
> # nrcpus avail : 24
> # cpudesc : AMD Ryzen 9 3900X 12-Core Processor
> # cpuid : AuthenticAMD,23,113,0
> # total memory : 32884432 kB
> # cmdline : /home/acme/bin/perf record ls 
> # event : name = cycles:u, , id = { 85540, 85541, 85542, 85543, 85544, 85545, 85546, 85547, 85548, 85549, 85550, 85551, 85552, 85553, 85554, 85555, 85556, 85557, 85558, 85559, 85560, 85561, 85562, 85563 }, size = 120, { sample_period, sample_freq } = 4000, sample_type = IP|TID|TIME|PERIOD, read_format = ID, disabled = 1, inherit = 1, exclude_kernel = 1, mmap = 1, comm = 1, freq = 1, enable_on_exec = 1, task = 1, sample_id_all = 1, exclude_guest = 1, mmap2 = 1, comm_exec = 1, ksymbol = 1, bpf_event = 1
> # CPU_TOPOLOGY info available, use -I to display
> # NUMA_TOPOLOGY info available, use -I to display
> # pmu mappings: amd_df = 8, software = 1, ibs_op = 11, power = 14, ibs_fetch = 10, uprobe = 7, cpu = 4, amd_iommu_0 = 12, breakpoint = 5, amd_l3 = 9, tracepoint = 2, kprobe = 6, msr = 13
> # CACHE info available, use -I to display
> # time of first sample : 12184.494971
> # time of last sample : 12184.495496
> # sample duration :      0.525 ms
> # MEM_TOPOLOGY info available, use -I to display
> # cpu pmu capabilities: max_precise=0
> # missing features: TRACING_DATA BRANCH_STACK GROUP_DESC AUXTRACE STAT CLOCKID DIR_FORMAT COMPRESSED CLOCK_DATA 
> # ========
> #
> 
> I.e. users would discover that using this control file is as easy as
> working with perf.data files or with the pipe mode, all the three ways
> of interacting with perf would use the same command interface arguments.

yep, I agree we can mimic the similar arguments, but I doubt we
can easily reuse the same code for that

jirka