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List:       busybox
Subject:    RE: fix large PID overflow their column in top command
From:       David Laight <David.Laight () ACULAB ! COM>
Date:       2023-11-23 17:10:01
Message-ID: 4458638ee54e4ae7a47a9586de9b874d () AcuMS ! aculab ! com
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...
> +       fp = xfopen_for_read("/proc/sys/kernel/pid_max");
> +       if (!fgets(pid_buf, PID_DIGITS_MAX + 1, fp)) {
> ...
> +       if (strncmp(pid_buf, "32768", 5) == 0)
> +               pid_digits_num = 5;
> +       else
> +               pid_digits_num = PID_DIGITS_MAX;
> 
> The logic above is not sound. Even if sysctl kernel.pid_max
> is 32768, there can be already running processes with pids > 99999.

It's also probably wrong for pretty much all other values.

I'd just base the column width on strlen(pid_buf) with a minimum
value of 5.

It is unlikely that pid_max has been reduced - so column overflow
it that case probably doesn't really matter.

The more interesting case is really a system with a very large pid_max
that has never run many processes.
You don't really want lots of blank space.

I can't remember whether top reads everything before doing any output?
Since the output is sorted it probably almost always does.
In which case it knows the column width it will need.

I did post a patch a while back that enabled 'Irix mode'.
(100% cpu is one cpu at 100%, not all cpus at 100%)
Maybe I should dig it out again.

	David

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