Re: [patch] procfs/procps threading performance speedup, 2.5.62

[miquels@cistron-office.nl (Miquel van Smoorenburg)]

In article <Pine.LNX.4.44.0302201656030.30000-100000@localhost.localdomain>,
Ingo Molnar  <mingo@elte.hu> wrote:
>the fix for this is two-fold. First, it must be possible for procps to
>separate 'threads' from 'processes' without having to go into 16 thousand
>directories. I solved this by prefixing 'threads' (ie. non-group-leader
>threads) with a dot ('.') character in the /proc listing:

Why not put threads belonging to a thread group into /proc/17072/threads ?

> $ ls -a /proc

I'm seeing 17072 as a group-leader and the 'threads' as .17073 etc.
When you put all 'threads' into /proc/17072/threads, you'd get
/proc/17072/threads/17072, /proc/17072/threads/17073, etc.
/proc/17072 would show stats for the whole threads group, while
/proc/17072/threads/17072 would show stats for just that thread.

>the .17073 ... .17082 entries belong to the thread-group 17072.

Yuck ;(

>The key here is for procps to be able to parse threads without having to
>call into the kernel 16K times. The dot-approach also has the added
>benefit of 'hiding' threads in the default 'ls /proc' listing.

What is against /proc/<pid>/threads ?

>the other change needed was the ability to read comulative CPU usage
>statistics from the thread group leader. I've introduced 4 new fields in
>/proc/PID/stat for that purpose, the kernel keeps those uptodate across
>fork/exit and in the timer interrupt - it's very low-overhead.

That would also be solved with /proc/<pid> and /proc/<pid>/threads/<thread>

>another advantage of this approach is that old procps is fully compatible
>with the new kernel, and new procps is fully compatible with old kernels.  

That would also be the case with /proc/<pid>/threads

Mike.
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