Re: [PATCH v2 03/15] perf data: open data directory in read access mode

Jiri Olsa
2020-10-27T11:59:21Z

On Mon, Oct 26, 2020 at 08:47:06PM +0300, Alexey Budankov wrote:
>
> On 24.10.2020 18:43, Jiri Olsa wrote:
> > On Wed, Oct 21, 2020 at 06:57:53PM +0300, Alexey Budankov wrote:
> >>
> >> Open files located at trace data directory in case read access
> >> mode is requested. File are opened and its fds assigned to
> >> perf_data dir files especially for loading data directories
> >> content in perf report mode.
> >>
> >> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> >> ---
> >> tools/perf/util/data.c | 4 ++++
> >> 1 file changed, 4 insertions(+)
> >>
> >> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> >> index c47aa34fdc0a..6ad61ac6ba67 100644
> >> --- a/tools/perf/util/data.c
> >> +++ b/tools/perf/util/data.c
> >> @@ -321,6 +321,10 @@ static int open_dir(struct perf_data *data)
> >> return -1;
> >>
> >> ret = open_file(data);
> >> + if (!ret && perf_data__is_dir(data)) {
> >> + if (perf_data__is_read(data))
> >> + ret = perf_data__open_dir(data);
> >> + }
> >
> > perf_data__open_dir is also called from perf_session__new
> > is it called twice?
>
> It is not called twice. It is in different branches.
> This one is for write and the other one is for read.

hum, is that right?

# ./perf record --threads
^C[ perf record: Woken up 15 times to write data ]
[ perf record: Captured and wrote 1.421 MB perf.data (515 samples) ]

# gdb ./perf
GNU gdb (GDB) Fedora 9.1-6.fc32

(gdb) b perf_data__open_dir
Breakpoint 1 at 0x5b4753: file util/data.c, line 72.

(gdb) r --no-pager report --stdio
Starting program: /home/jolsa/kernel/linux-perf/tools/perf/perf --no-pager report --stdio

Breakpoint 1, perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
72 {
(gdb) bt
#0 perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
#1 0x00000000005b538d in open_dir (data=0x7fffffffb0e0) at util/data.c:326
#2 0x00000000005b546d in perf_data__open (data=0x7fffffffb0e0) at util/data.c:351
#3 0x00000000005627e8 in perf_session__new (data=0x7fffffffb0e0, repipe=false, tool=0x7fffffffb220) at util/session.c:210
#4 0x000000000045a572 in cmd_report (argc=0, argv=0x7fffffffd7a8) at builtin-report.c:1372
#5 0x00000000004f49ec in run_builtin (p=0xaadab0 <commands+240>, argc=2, argv=0x7fffffffd7a8) at perf.c:312
#6 0x00000000004f4c59 in handle_internal_command (argc=2, argv=0x7fffffffd7a8) at perf.c:364
#7 0x00000000004f4da0 in run_argv (argcp=0x7fffffffd5ec, argv=0x7fffffffd5e0) at perf.c:408
#8 0x00000000004f516c in main (argc=2, argv=0x7fffffffd7a8) at perf.c:538

(gdb) c
Continuing.

Breakpoint 1, perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
72 {
(gdb) bt
#0 perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
#1 0x0000000000562883 in perf_session__new (data=0x7fffffffb0e0, repipe=false, tool=0x7fffffffb220) at util/session.c:234
#2 0x000000000045a572 in cmd_report (argc=0, argv=0x7fffffffd7a8) at builtin-report.c:1372
#3 0x00000000004f49ec in run_builtin (p=0xaadab0 <commands+240>, argc=2, argv=0x7fffffffd7a8) at perf.c:312
#4 0x00000000004f4c59 in handle_internal_command (argc=2, argv=0x7fffffffd7a8) at perf.c:364
#5 0x00000000004f4da0 in run_argv (argcp=0x7fffffffd5ec, argv=0x7fffffffd5e0) at perf.c:408
#6 0x00000000004f516c in main (argc=2, argv=0x7fffffffd7a8) at perf.c:538

AFAICS the second (current) call to perf_data__open_dir will
do the job, because the call you added still does not see
directory with proper version and will bail out on call to
perf_data__is_single_file

perf_session__open call will read headers and update dir version
so the current perf_data__open_dir will open the directory

jirka