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From: Wang Nan <wangnan0@huawei.com>
To: <linux-kernel@vger.kernel.org>, <kan.liang@intel.com>,
	<acme@kernel.org>, <jolsa@redhat.com>, <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Subject: [PATCH v2 6/8] perf mmap: Fix perf backward recording
Date: Sun, 3 Dec 2017 02:00:42 +0000	[thread overview]
Message-ID: <20171203020044.81680-7-wangnan0@huawei.com> (raw)
In-Reply-To: <20171203020044.81680-1-wangnan0@huawei.com>

perf record backward recording doesn't work as we expected: it never
overwrite when ring buffer full.

Test:

(Run a busy printing task background like this:

 while True:
     print 123

send SIGUSR2 to perf to capture snapshot.)

 # ./perf record --overwrite -e raw_syscalls:sys_enter -e raw_syscalls:sys_exit --exclude-perf -a --switch-output
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101520743 ]
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101521251 ]
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101521692 ]
 ^C[ perf record: Woken up 1 times to write data ]
 [ perf record: Dump perf.data.2017110101521936 ]
 [ perf record: Captured and wrote 0.826 MB perf.data.<timestamp> ]

 # ./perf script -i ./perf.data.2017110101520743 | head -n3
             perf  2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0)
             perf  2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0)
           python  2545 [000] 12449.310800:  raw_syscalls:sys_exit: NR 1 = 4
 # ./perf script -i ./perf.data.2017110101521251 | head -n3
             perf  2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0)
             perf  2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0)
           python  2545 [000] 12449.310800:  raw_syscalls:sys_exit: NR 1 = 4
 # ./perf script -i ./perf.data.2017110101521692 | head -n3
             perf  2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0)
             perf  2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0)
           python  2545 [000] 12449.310800:  raw_syscalls:sys_exit: NR 1 = 4

Timestamps are never change, but my background task is a dead loop, can
easily overwhelme the ring buffer.

This patch fix it by force unsetting PROT_WRITE for backward ring
buffer, so all backward ring buffer become overwrite ring buffer.

Test result:

 # ./perf record --overwrite -e raw_syscalls:sys_enter -e raw_syscalls:sys_exit --exclude-perf -a --switch-output
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101285323 ]
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101290053 ]
 [ perf record: dump data: Woken up 1 times ]
 [ perf record: Dump perf.data.2017110101290446 ]
 ^C[ perf record: Woken up 1 times to write data ]
 [ perf record: Dump perf.data.2017110101290837 ]
 [ perf record: Captured and wrote 0.826 MB perf.data.<timestamp> ]
 # ./perf script -i ./perf.data.2017110101285323 | head -n3
           python  2545 [000] 11064.268083:  raw_syscalls:sys_exit: NR 1 = 4
           python  2545 [000] 11064.268084: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0)
           python  2545 [000] 11064.268086:  raw_syscalls:sys_exit: NR 1 = 4
 # ./perf script -i ./perf.data.2017110101290 | head -n3
 failed to open ./perf.data.2017110101290: No such file or directory
 # ./perf script -i ./perf.data.2017110101290053 | head -n3
           python  2545 [000] 11071.564062: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0)
           python  2545 [000] 11071.564064:  raw_syscalls:sys_exit: NR 1 = 4
           python  2545 [000] 11071.564066: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0)
 # ./perf script -i ./perf.data.2017110101290 | head -n3
 perf.data.2017110101290053  perf.data.2017110101290446  perf.data.2017110101290837
 # ./perf script -i ./perf.data.2017110101290446 | head -n3
             sshd  1321 [000] 11075.499473:  raw_syscalls:sys_exit: NR 14 = 0
             sshd  1321 [000] 11075.499474: raw_syscalls:sys_enter: NR 14 (2, 7ffe98899490, 0, 8, 0, 3000)
             sshd  1321 [000] 11075.499474:  raw_syscalls:sys_exit: NR 14 = 0
 # ./perf script -i ./perf.data.2017110101290837 | head -n3
           python  2545 [000] 11079.280844:  raw_syscalls:sys_exit: NR 1 = 4
           python  2545 [000] 11079.280847: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0)
           python  2545 [000] 11079.280850:  raw_syscalls:sys_exit: NR 1 = 4

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
 tools/perf/util/evlist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 68c1f95..bb70aef 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -799,7 +799,7 @@ perf_evlist__should_poll(struct perf_evlist *evlist __maybe_unused,
 }
 
 static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
-				       struct mmap_params *mp, int cpu_idx,
+				       struct mmap_params mp, int cpu_idx,
 				       int thread, int *_output, int *_output_backward)
 {
 	struct perf_evsel *evsel;
@@ -824,6 +824,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 				if (evlist->bkw_mmap_state == BKW_MMAP_NOTREADY)
 					perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_RUNNING);
 			}
+			mp.prot &= ~PROT_WRITE;
 		}
 
 		if (evsel->system_wide && thread)
@@ -838,7 +839,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 		if (*output == -1) {
 			*output = fd;
 
-			if (perf_mmap__mmap(&maps[idx], mp, *output)  < 0)
+			if (perf_mmap__mmap(&maps[idx], &mp, *output)  < 0)
 				return -1;
 		} else {
 			if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0)
@@ -890,7 +891,7 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist,
 					      true);
 
 		for (thread = 0; thread < nr_threads; thread++) {
-			if (perf_evlist__mmap_per_evsel(evlist, cpu, mp, cpu,
+			if (perf_evlist__mmap_per_evsel(evlist, cpu, *mp, cpu,
 							thread, &output, &output_backward))
 				goto out_unmap;
 		}
@@ -917,7 +918,7 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist,
 		auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, thread,
 					      false);
 
-		if (perf_evlist__mmap_per_evsel(evlist, thread, mp, 0, thread,
+		if (perf_evlist__mmap_per_evsel(evlist, thread, *mp, 0, thread,
 						&output, &output_backward))
 			goto out_unmap;
 	}
-- 
2.10.1

  parent reply	other threads:[~2017-12-03  2:03 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-03  2:00 [PATCH v2 0/8] perf tools: perf tools: Clarify overwrite and backward, bugfix Wang Nan
2017-12-03  2:00 ` [PATCH v2 1/8] perf tools: Remove 'overwrite' parameter from perf_evlist__mmap Wang Nan
2017-12-06 16:41   ` [tip:perf/core] perf evlist: " tip-bot for Wang Nan
2017-12-03  2:00 ` [PATCH v2 2/8] perf tools: Remove 'overwrite' parameter from perf_evlist__mmap_ex Wang Nan
2017-12-06 16:41   ` [tip:perf/core] perf evlist: " tip-bot for Wang Nan
2017-12-03  2:00 ` [PATCH v2 3/8] perf tools: Remove evlist->overwrite Wang Nan
2017-12-06 16:42   ` [tip:perf/core] perf evlist: " tip-bot for Wang Nan
2017-12-03  2:00 ` [PATCH v2 4/8] perf tools: Remove overwrite from arguments list of perf_mmap__push Wang Nan
2017-12-06 16:42   ` [tip:perf/core] perf mmap: " tip-bot for Wang Nan
2017-12-03  2:00 ` [PATCH v2 5/8] perf tools: Remove overwrite and check_messup from mmap read Wang Nan
2017-12-06 16:42   ` [tip:perf/core] perf mmap: " tip-bot for Wang Nan
2017-12-03  2:00 ` Wang Nan [this message]
2017-12-04  5:37   ` [PATCH v2 6/8] perf mmap: Fix perf backward recording Namhyung Kim
2017-12-04 15:44     ` Arnaldo Carvalho de Melo
2017-12-03  2:00 ` [PATCH v2 7/8] perf tools: Don't discard prev in backward mode Wang Nan
2017-12-03  2:00 ` [PATCH v2 8/8] perf tools: Replace 'backward' to 'overwrite' in evlist, mmap and record Wang Nan
2017-12-04  5:39 ` [PATCH v2 0/8] perf tools: perf tools: Clarify overwrite and backward, bugfix Namhyung Kim

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