16 May
2008
16 May
'08
2:27 p.m.
After a forum discussion, I've found that chrt does not seem to be working.
(At least not on my system or on the systems of the others involved)
Specifically, it doesn't seem like it can be used to launch a program using a
scheduling policy other than SCHED_OTHER.
It does work if I change the scheduling policy of a process after the process
is already started, but it doesn't seem to work when using it to start a
process.
Something like "chrt -f 40 foobar" still starts foobar using the SCHED_OTHER
policy. Is this a known issue?
-Reuben
10:25 p.m.
Back on Saturday 17 May 2008, Ray Rashif was like:
With htop, do you see "-41" as the priority?
Ah-ha! With htop I see 4 separate jackd processes shown with different
priorties. One of them with "-41" as priority.
I was using either
ps -elH | grep jackd
or
chrt -p `pidof jackd`
to see what how the scheduling was set up. Apparently there are sub-processes
or something of that nature that isn't listed with the first command?
And "pidof jackd" obviously returns the pid of the first process it finds.
I guess I just wasn't aware that there are 4 separate jackd processes that
run. That makes a lot more sense now.
Thanks for the tip!
-Reuben
18 May
18 May
7:44 p.m.
On Sat, 2008-05-17 at 19:12 -0500, Reuben Martin wrote:
I guess I just wasn't aware that there are 4
separate jackd processes that
run. That makes a lot more sense now.
terminology (simplified)
"TASK" : a kernel-level thread
"THREAD" : a user-space thread
"PROCESS" : 1 or more threads, plus an
address space and a file table
JACK is a single process involving multiple threads.
--p
11:56 p.m.
Back on Sunday 18 May 2008, Paul Davis was like:
On Sat, 2008-05-17 at 19:12 -0500, Reuben Martin
wrote:
Why then are the threads assigned separate PIDs? I was under the assumption
that PID stood for "Process Identifier". (Perhaps "Posix thread
IDentifier"
would be a better definition of the acronym) I was totally unaware that you
could assign process threads separate scheduling priorities / policies apart
from the parent process.
Also, is it possible (within the context of programming) to assign threads
individual names to give an indication as to what the specific PID is doing,
or are thread PID names always named the same as the parent process?
I'm sure these questions open up a whole can of worms dealing with the mess of
conforming modern programming concepts to an aging POSIX framework.
-Reuben
I guess I just wasn't aware that there are 4
separate jackd processes
that run. That makes a lot more sense now.
terminology (simplified)
"TASK" : a kernel-level thread
"THREAD" : a user-space thread
"PROCESS" : 1 or more threads, plus an
address space and a file table
JACK is a single process involving multiple threads.
--p 
19 May
19 May
1:36 a.m.
Reuben Martin wrote:
Why then are the threads assigned separate PIDs?
This is a byproduct of how threads are implemented in the Linux kernel;
they are just separate processes which share the same address map. The
way Linux does it is simpler that some other OSes which have separate
code to handle threads within a process vs processes themselves.
I was under the assumption
that PID stood for "Process Identifier".
Correct.
(Perhaps "Posix thread IDentifier"
would be a better definition of the acronym) I was totally unaware that you
could assign process threads separate scheduling priorities / policies apart
from the parent process.
I think this is even a requirement for POSIX.
Also, is it possible (within the context of
programming) to assign threads
individual names to give an indication as to what the specific PID is doing,
or are thread PID names always named the same as the parent process?
Not sure.
I'm sure these questions open up a whole can of
worms dealing with the mess of
conforming modern programming concepts to an aging POSIX framework.
What can of worms? What mess?
Quite honestly I think POSIX is showing far less signs of age that many
other far younger APIs (win32 I'm looking at you).
Erik
--
-----------------------------------------------------------------
Erik de Castro Lopo
-----------------------------------------------------------------
"Java, the best argument for Smalltalk since C++." -- Frank Winkler
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5 comments
4 participants
participants (4)
-
Erik de Castro Lopo -
Paul Davis -
Ray Rashif -
Reuben Martin