Re: [PATCH v3 3/4] perf record: Don't clear event's period if set by a term

On Mon, Sep 14, 2020 at 2:51 PM Arnaldo Carvalho de Melo
[off-list ref] wrote:

Em Mon, Sep 14, 2020 at 06:46:55PM -0300, Arnaldo Carvalho de Melo escreveu:

quoted

Em Fri, Sep 11, 2020 at 07:56:54PM -0700, Ian Rogers escreveu:

quoted

If events in a group explicitly set a frequency or period with leader
sampling, don't disable the samples on those events.

Prior to 5.8:
perf record -e '{cycles/period=12345000/,instructions/period=6789000/}:S'
would clear the attributes then apply the config terms. In commit
5f34278867b7 leader sampling configuration was moved to after applying the
config terms, in the example, making the instructions' event have its period
cleared.
This change makes it so that sampling is only disabled if configuration
terms aren't present.

Adrian, Jiri, can you please take a look a this and provide Reviewed-by
or Acked-by tags?

Without this patch we have:

# perf record -e '{cycles/period=1/,instructions/period=2/}:S' sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.051 MB perf.data (6 samples) ]
#
# perf evlist -v
cycles/period=1/: size: 120, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, disabled: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
instructions/period=2/: size: 120, config: 0x1, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, sample_id_all: 1, exclude_guest: 1
#

So indeed the period=2 is being cleared for the second event in that
group.

- Arnaldo

Thanks Arnaldo and Adrian! Adrian's acked-by is here:
https://lore.kernel.org/lkml/77df85d3-a50c-d6aa-1d60-4fc9ea90dc44@intel.com/ (local)
Let me know if anything is missing.

Ian