new 'read' trigger action about uftrace

[namhyung]

@honggyukim @Taeung I added --opt-file option (66c6869).

[honggyukim]

This is the feature I was waiting for. One of the main purpose of python scripting was to read system wide stats such as rss, but this can handle it better in some specific cases. I also want to run 'read' trigger at the function exit as you mentioned, so we need to think about the interface.

It may be another issue but I would like to simplify some options and trigger actions. Currently, -A serves only for arguments, -R serves only for return values, and -T is for other triggering options at the entry of function. And -F can also provide some trigger actions. Sometimes, I have to provide the same function name many times to provides it to each -A, -R, -T, -F option. We may have to make those simpler way to reduce the repetition.

[honggyukim]

One more question is that I'm wondering if maxrss from rusage is the same rss information that can be read from /proc/[pid]/stat. I thought that it's the maximum value.

[Taeung]

@honggyukim , I also thought the spot of bother you said above.
So we need to implement the config feature for it ?

I thought we can make the config feature like menuconfig of linux kernel IMHO,
and if we do, the config feature(TUI) can utilize symbol information from target program,
but I'm not sure it is great way.. hum..

[namhyung]

@honggyukim I agree that repeating names for each option is not a great way. Maybe we can just use -T and -R for entry/exit time trigger and provides -F, -N and -A for simpler interface (and compatibility). Thoughts?

[namhyung]

@Taeung I don't know what do you want to do with the config interface. Do you want to specify functions and their triggers in a config file?

[honggyukim]

@Taeung It would be great if we can pass a config file for those setup. I mentioned that we could provide options with $(< config) but it's shell dependent so I prefer to have a config file that contains all the options that we can pass to uftrace. I thought about the structure json like format but it could be anything.

[namhyung]

Some tools provide a way to read options from a file directly. For example, gcc supports @file option for this.

[Taeung]

@namhyung , Yes, the config interface I said is for a particular target program, not overall.
I thought if we apply the config interface,
the user can temporally set various options (e.g. trigger, event, filter, arguments, etc.)
with given function names on TUI before recording target execution.

Hum.. temporary setup(to prepare various options) before recording a particular target program ?
or,
As @honggyukim said, if we enable the user to pass a config file for those setup,
additionally I thought uftrace tool can generate a skeleton config file for the user.

But they can be needless, if uftrace tool support the way to read options from a file.. as you said.

[namhyung]

Update to review/trigger-read-v2.

Changelog:

• change name to 'proc.statm' to clarify it's reading memory stats from /proc/self/statm
• add 'proc.page-fault' to show page faults
• fix segfault when more than 4 events before saving to shmbuf
• fix a bug on parsing regex pattern
• drop event after fork()

Example:

$ uftrace  -T b@read=proc.statm  t-abc
# DURATION    TID     FUNCTION
            [32417] | main() {
            [32417] |   a() {
            [32417] |     b() {
            [32417] |       /* read:proc.statm (size=6810KB, rss=785KB, shared=719KB) */
            [32417] |       c() {
   0.479 us [32417] |         getpid();
   3.014 us [32417] |       } /* c */
  16.914 us [32417] |     } /* b */
  17.083 us [32417] |   } /* a */
  17.873 us [32417] | } /* main */

$ uftrace  -T b@read=proc.page-fault  t-abc
# DURATION    TID     FUNCTION
            [32766] | main() {
            [32766] |   a() {
            [32766] |     b() {
            [32766] |       /* read:proc.page-fault (major=0, minor=188) */
            [32766] |       c() {
   0.609 us [32766] |         getpid();
  13.722 us [32766] |       } /* c */
  24.950 us [32766] |     } /* b */
  25.564 us [32766] |   } /* a */
  26.963 us [32766] | } /* main */

[namhyung]

Update to review/trigger-read-v3.

Changelog:

• rename to "proc/statm" and "page-fault"
• honor color setting

Example:

$ uftrace  -T b@read=proc/statm,color=green  t-abc
# DURATION    TID     FUNCTION
   0.819 us [17908] | __monstartup();
   0.475 us [17908] | __cxa_atexit();
            [17908] | main() {
            [17908] |   a() {
            [17908] |     b() {
            [17908] |       /* read:proc/statm (size=6809KB, rss=765KB, shared=701KB) */
            [17908] |       c() {
   0.602 us [17908] |         getpid();
   2.148 us [17908] |       } /* c */
  21.077 us [17908] |     } /* b */
  21.391 us [17908] |   } /* a */
  21.743 us [17908] | } /* main */

$ uftrace  -T b@read=page-fault  t-abc
# DURATION    TID     FUNCTION
   1.167 us [31503] | __monstartup();
   0.870 us [31503] | __cxa_atexit();
            [31503] | main() {
            [31503] |   a() {
            [31503] |     b() {
            [31503] |       /* read:page-fault (major=0, minor=189) */
            [31503] |       c() {
   0.772 us [31503] |         getpid();
   2.780 us [31503] |       } /* c */
   8.254 us [31503] |     } /* b */
   8.661 us [31503] |   } /* a */
   9.212 us [31503] | } /* main */