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From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>,
	linux-kernel@vger.kernel.org, kan.liang@intel.com,
	jolsa@redhat.com, kernel-team@lge.com
Subject: Re: [PATCH v2 6/8] perf mmap: Fix perf backward recording
Date: Mon, 4 Dec 2017 12:44:02 -0300	[thread overview]
Message-ID: <20171204154402.GC13698@kernel.org> (raw)
In-Reply-To: <20171204053744.GA16360@sejong>

Em Mon, Dec 04, 2017 at 02:37:44PM +0900, Namhyung Kim escreveu:
> Hi,
> 
> On Sun, Dec 03, 2017 at 02:00:42AM +0000, Wang Nan wrote:
> > 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;
> >
> 
> I still prefer updating mp->prot based on evsel->attr.write_backward
> here (instead of passing mp as value).  It'd create a minimal change.

Wang? I applied 1-5 in this series, waiting now for this to settle,

- Arnaldo

  reply	other threads:[~2017-12-04 15:44 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 ` [PATCH v2 6/8] perf mmap: Fix perf backward recording Wang Nan
2017-12-04  5:37   ` Namhyung Kim
2017-12-04 15:44     ` Arnaldo Carvalho de Melo [this message]
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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