linux-kernel - [PATCH 37/57] perf trace: Honour --max-events in processing syscalls:sys_enter

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Message-Id: <20191021133834.25998-38-acme@kernel.org>
Date:   Mon, 21 Oct 2019 10:38:14 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>,
        Luis Cláudio Gonçalves 
        <lclaudio@...hat.com>
Subject: [PATCH 37/57] perf trace: Honour --max-events in processing syscalls:sys_enter_*

From: Arnaldo Carvalho de Melo <acme@...hat.com>

We were doing this only at the sys_exit syscall tracepoint, as for
strace-like we count the pair of sys_enter and sys_exit as one event,
but when asking specifically for a the syscalls:sys_enter_NAME
tracepoint we need to count each of those as an event.

I.e. things like:

  # perf trace --max-events=4 -e syscalls:sys_enter_lseek
     0.000 pool/2242 syscalls:sys_enter_lseek(fd: 14<anon_inode:[timerfd]>, offset: 0, whence: CUR)
     0.034 pool/2242 syscalls:sys_enter_lseek(fd: 15<anon_inode:[timerfd]>, offset: 0, whence: CUR)
     0.051 pool/2242 syscalls:sys_enter_lseek(fd: 16<anon_inode:[timerfd]>, offset: 0, whence: CUR)
  2307.900 sshd/30800 syscalls:sys_enter_lseek(fd: 3</usr/lib64/libsystemd.so.0.25.0>, offset: 9032, whence: SET)
  #

Were going on forever, since we only had sys_enter events.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: https://lkml.kernel.org/n/tip-0ob1dky1a9ijlfrfhxyl40wr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-trace.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 0294b17ed510..1aaf7b28eec4 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2727,12 +2727,6 @@ static int trace__event_handler(struct trace *trace, struct evsel *evsel,
 			} else {
 				trace__fprintf_tp_fields(trace, evsel, sample, thread, NULL, 0);
 			}
-			++trace->nr_events_printed;
-
-			if (evsel->max_events != ULONG_MAX && ++evsel->nr_events_printed == evsel->max_events) {
-				evsel__disable(evsel);
-				evsel__close(evsel);
-			}
 		}
 	}
 
@@ -2743,6 +2737,13 @@ static int trace__event_handler(struct trace *trace, struct evsel *evsel,
 		trace__fprintf_callchain(trace, sample);
 	else if (callchain_ret < 0)
 		pr_err("Problem processing %s callchain, skipping...\n", perf_evsel__name(evsel));
+
+	++trace->nr_events_printed;
+
+	if (evsel->max_events != ULONG_MAX && ++evsel->nr_events_printed == evsel->max_events) {
+		evsel__disable(evsel);
+		evsel__close(evsel);
+	}
 out:
 	thread__put(thread);
 	return 0;
-- 
2.21.0