Re: [PATCH] ftrace: fix task's invalid comm of <...> when big pid

[Wang Yu]

å 18/3/29 äå10:26, Steven Rostedt åé:
> On Thu, 29 Mar 2018 10:16:22 +0800
> Wang Yu <yuwang@xxxxxxxxxxxxxxxxx> wrote:
>
> > > What you can do is make that map_pid_to_cmdline array bigger.
> > >
> > > -- Steve
> > I am sorry about it, and as the number of cpu cores increases, the current
> >
> > PID_MAX_DEFAULT is too small, our online machines set the pid_max 65536 as default, so the task
> > pid number bigger than PID_MAX_DEFAULT can't show the real comm (only <...>), so i want to
> > ajust the PID_MAX_DEFAULT upto 4x, and what do you think?
> >
> >     * This controls the default maximum pid allocated to a process
> >     */
> > -#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
> > +#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x20000)
> What I was thinking is to make the map_pid_to_cmdline array dynamic
> (not static), and be set to pid_max (after pid_max is determined).
>
> Now, pid_max can be changed at run time. Thus, the tracing code will
> need to keep a separate variable for that array to store the length. It
> can not rely on pid_max. But if a pid that is greater than pid_max is
> found, we could kick off a work thread to increase the array.
thanks for your reply, thanks, if map_pid_to_cmdline need dynamic, 
saved_cmdlines_buffer