linux-toradex.git/tools/lib/api/fs, branch v6.3-rc5

tracing: Always use canonical ftrace path

2023-02-18T19:34:09+00:00

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com

Acked-by: Masami Hiramatsu (Google) 
Reviewed-by: Mukesh Ojha 
Signed-off-by: Ross Zwisler 
Signed-off-by: Steven Rostedt (Google)

tools lib api fs tracing_path: Add scandir alphasort

2022-11-15T13:24:09+00:00

tracing_events__opendir() allows iteration over files in
/tracing/events but with an arbitrary sort order.

Add a scandir alternative where the results are alphabetically sorted.

Signed-off-by: Ian Rogers 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Caleb Biggers 
Cc: Jiri Olsa 
Cc: Kajol Jain 
Cc: Kan Liang 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Perry Taylor 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Rob Herring 
Cc: Sandipan Das 
Cc: Stephane Eranian 
Cc: Weilin Wang 
Cc: Xin Gao 
Cc: Xing Zhengjun 
Link: http://lore.kernel.org/lkml/20221114210723.2749751-4-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Cache cgroupfs mount point

2021-02-17T18:09:08+00:00

Currently it parses the /proc file everytime it opens a file in the
cgroupfs.  Save the last result to avoid it (assuming it won't be
changed between the accesses).

Signed-off-by: Namhyung Kim 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Jiri Olsa 
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lore.kernel.org/lkml/20201216090556.813996-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Diet cgroupfs_find_mountpoint()

2021-02-17T18:08:32+00:00

Reduce the number of buffers and hopefully make it more efficient. :)

Signed-off-by: Namhyung Kim 
Acked-by: Jiri Olsa 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lore.kernel.org/lkml/20201216090556.813996-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Prefer cgroup v1 path in cgroupfs_find_mountpoint()

2021-02-17T18:06:22+00:00

The cgroupfs_find_mountpoint() looks up the /proc/mounts file to find
a directory for the given cgroup subsystem.  It keeps both cgroup v1
and v2 path since there's a possibility of the mixed hierarchly.

But we can simply use v1 path if it's found as it will override the v2
hierarchy.

Signed-off-by: Namhyung Kim 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Jiri Olsa 
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lore.kernel.org/lkml/20201216090556.813996-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Make xxx__mountpoint() more scalable

2020-04-16T15:19:12+00:00

The xxx_mountpoint() interface provided by fs.c finds mount points for
common pseudo filesystems. The first time xxx_mountpoint() is invoked,
it scans the mount table (/proc/mounts) looking for a match. If found,
it is cached. The price to scan /proc/mounts is paid once if the mount
is found.

When the mount point is not found, subsequent calls to xxx_mountpoint()
scan /proc/mounts over and over again.  There is no caching.

This causes a scaling issue in perf record with hugeltbfs__mountpoint().
The function is called for each process found in
synthesize__mmap_events().  If the machine has thousands of processes
and if the /proc/mounts has many entries this could cause major overhead
in perf record. We have observed multi-second slowdowns on some
configurations.

As an example on a laptop:

Before:

  $ sudo umount /dev/hugepages
  $ strace -e trace=openat -o /tmp/tt perf record -a ls
  $ fgrep mounts /tmp/tt
  285

After:

  $ sudo umount /dev/hugepages
  $ strace -e trace=openat -o /tmp/tt perf record -a ls
  $ fgrep mounts /tmp/tt
  1

One could argue that the non-caching in case the moint point is not
found is intentional. That way subsequent calls may discover a moint
point if the sysadmin mounts the filesystem. But the same argument could
be made against caching the mount point. It could be unmounted causing
errors.  It all depends on the intent of the interface. This patch
assumes it is expected to scan /proc/mounts once. The patch documents
the caching behavior in the fs.h header file.

An alternative would be to just fix perf record. But it would solve the
problem with hugetlbs__mountpoint() but there could be similar issues
(possibly down the line) with other xxx_mountpoint() calls in perf or
other tools.

Signed-off-by: Stephane Eranian 
Reviewed-by: Ian Rogers 
Acked-by: Jiri Olsa 
Cc: Alexander Shishkin 
Cc: Andrey Zhizhikin 
Cc: Kan Liang 
Cc: Kefeng Wang 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Thomas Gleixner 
Link: http://lore.kernel.org/lkml/20200402154357.107873-3-irogers@google.com
Signed-off-by: Ian Rogers 
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs: Move cgroupsfs_find_mountpoint()

2020-03-04T13:34:09+00:00

Move it from tools/perf/util/cgroup.c as it can be used by other places.
Note that cgroup filesystem is different from others since it's usually
mounted separately (in v1) for each subsystem.

I just copied the code with a little modification to pass a name of
subsystem.

Suggested-by: Jiri Olsa 
Signed-off-by: Namhyung Kim 
Cc: Jiri Olsa 
Link: http://lore.kernel.org/lkml/20200127100031.1368732-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs: Fix gcc9 stringop-truncation compilation error

2020-01-06T14:46:09+00:00

GCC9 introduced string hardening mechanisms, which exhibits the error
during fs api compilation:

error: '__builtin_strncpy' specified bound 4096 equals destination size
[-Werror=stringop-truncation]

This comes when the length of copy passed to strncpy is is equal to
destination size, which could potentially lead to buffer overflow.

There is a need to mitigate this potential issue by limiting the size of
destination by 1 and explicitly terminate the destination with NULL.

Signed-off-by: Andrey Zhizhikin 
Reviewed-by: Petr Mladek 
Acked-by: Jiri Olsa 
Cc: Alexei Starovoitov 
Cc: Andrii Nakryiko 
Cc: Daniel Borkmann 
Cc: Kefeng Wang 
Cc: Martin KaFai Lau 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Song Liu 
Cc: Yonghong Song 
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/20191211080109.18765-1-andrey.zhizhikin@leica-geosystems.com
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: Renaming pr_warning to pr_warn

2019-10-18T13:02:57+00:00

For kernel logging macro, pr_warning is completely removed and
replaced by pr_warn, using pr_warn in tools lib api for symmetry
to kernel logging macro, then we could drop pr_warning in the
whole linux code.

Changing __pr_warning to __pr_warn to be consistent.

Link: http://lkml.kernel.org/r/20191018031850.48498-30-wangkefeng.wang@huawei.com
To: linux-kernel@vger.kernel.org
Cc: Arnaldo Carvalho de Melo 
Signed-off-by: Kefeng Wang 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek

perf tools: Fix tracing_path_mount proper path

2018-10-16T15:27:46+00:00

If there's no tracefs (RHEL7) support the tracing_path_mount
returns debugfs path which results in following fail:

  # perf probe sys_write
  kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENTS.
  Error: Failed to add events.

In tracing_path_debugfs_mount function we need to return the
'tracing' path instead of just the mount to make it work:

  # perf probe sys_write
  Added new event:
    probe:sys_write      (on sys_write)

  You can now use it in all perf tools, such as:

          perf record -e probe:sys_write -aR sleep 1

Adding the 'return tracing_path;' also to tracing_path_tracefs_mount
function just for consistency with tracing_path_debugfs_mount.

Upstream keeps working, because it has the tracefs support.

Link: http://lkml.kernel.org/n/tip-yiwkzexq9fk1ey1xg3gnjlw4@git.kernel.org
Signed-off-by: Jiri Olsa 
Cc: Alexander Shishkin 
Cc: Michael Petlan 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Fixes: 23773ca18b39 ("perf tools: Make perf aware of tracefs")
Link: http://lkml.kernel.org/r/20181016114818.3595-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo