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Date: Fri, 18 Nov 2022 13:34:03 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ian Rogers <irogers@...gle.com>,
Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Steven Rostedt <rostedt@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Linux Trace Devel <linux-trace-devel@...r.kernel.org>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v1 1/2] perf build: Require libtraceevent from the system
Em Fri, Nov 18, 2022 at 10:33:02AM -0500, Steven Rostedt escreveu:
> On Fri, 18 Nov 2022 12:02:38 -0300 Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> > yeah, this probably should work like with other libraries, don't stop
> > the build, just don't build features that depend on libtraceevent,
> > warning the user that features foo, bar and baz won't be available.
> > For people working with just hardware, software, cache events, no
> > problem.
> How are software events parsed?
Not parsed, fixed:
root@...-rk3399-pc:~# perf list sw
List of pre-defined events (to be used in -e or -M):
alignment-faults [Software event]
bpf-output [Software event]
cgroup-switches [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]
duration_time [Tool event]
user_time [Tool event]
system_time [Tool event]
root@...-rk3399-pc:~#
In addition to:
root@...-rk3399-pc:~# perf list hw
List of pre-defined events (to be used in -e or -M):
branch-instructions OR branches [Hardware event]
branch-misses [Hardware event]
bus-cycles [Hardware event]
cache-misses [Hardware event]
cache-references [Hardware event]
cpu-cycles OR cycles [Hardware event]
instructions [Hardware event]
root@...-rk3399-pc:~#
And:
root@...-rk3399-pc:~# perf list cache
List of pre-defined events (to be used in -e or -M):
L1-dcache-load-misses [Hardware cache event]
L1-dcache-loads [Hardware cache event]
L1-dcache-prefetch-misses [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]
branch-load-misses [Hardware cache event]
branch-loads [Hardware cache event]
dTLB-load-misses [Hardware cache event]
dTLB-store-misses [Hardware cache event]
iTLB-load-misses [Hardware cache event]
node-loads [Hardware cache event]
node-stores [Hardware cache event]
root@...-rk3399-pc:~#
Without something like libtraceevent 'perf probe', 'perf trace' wouldn't
work as of now, as it currently use libtraceevent to parse whats in
tracefs.
So for some people, just interested in profiling the above hw, sw and
cache events, libtraceevent isn't strictly required and may even be
desirable to reduce the number of library dependencies.
So its a valid feature to allow perf to be built without libtraceevent,
i.e. not something needed for the above scenarios.
With libbpf and BTF tracefs isn't also strictly needed, as we already
have to link with it and things like 'perf trace' want to use libbpf's
btf pretty printing stuff, we can use BTF to enumerate events, iterate
thru its fields, offsets, types, etc:
root@...-rk3399-pc:~# pahole --sizes | grep trace_event_raw_sched
trace_event_raw_sched_kthread_stop 28 0
trace_event_raw_sched_kthread_stop_ret 12 0
trace_event_raw_sched_kthread_work_queue_work 32 0
trace_event_raw_sched_kthread_work_execute_start 24 0
trace_event_raw_sched_kthread_work_execute_end 24 0
trace_event_raw_sched_wakeup_template 36 0
trace_event_raw_sched_switch 64 0
trace_event_raw_sched_migrate_task 40 0
trace_event_raw_sched_process_template 32 0
trace_event_raw_sched_process_wait 32 0
trace_event_raw_sched_process_fork 48 0
trace_event_raw_sched_process_exec 20 0
trace_event_raw_sched_stat_runtime 48 1
trace_event_raw_sched_pi_setprio 36 0
trace_event_raw_sched_move_numa 36 0
trace_event_raw_sched_numa_pair_template 48 0
trace_event_raw_sched_wake_idle_without_ipi 12 0
root@...-rk3399-pc:~#
root@...-rk3399-pc:~# pahole trace_event_raw_sched_switch
struct trace_event_raw_sched_switch {
struct trace_entry ent; /* 0 8 */
char prev_comm[16]; /* 8 16 */
pid_t prev_pid; /* 24 4 */
int prev_prio; /* 28 4 */
long int prev_state; /* 32 8 */
char next_comm[16]; /* 40 16 */
pid_t next_pid; /* 56 4 */
int next_prio; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
char __data[]; /* 64 0 */
/* size: 64, cachelines: 1, members: 9 */
};
root@...-rk3399-pc:~#
- Arnaldo
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