[nuby] about ruby multithreading

[Lionel Thiry]

Hello!
I need help:
Is Ruby multithreading cooperative or preemptive?

I mean: am I forced to abuse of Thread.pass in (every heavy) threads or
may I just assume the ruby interpreter will commute threads itself?

Another question:
Is Ruby multithreading blocked by system calls?

Like for example when calling system("command line").

If "no" to any of these questions, can I expect Ruby to work that way
someday?

Thanks for the help,
Lionel Thiry

 

[James Edward Gray II]

Hello!
I need help:
Is Ruby multithreading cooperative or preemptive?
Preemptive.

I mean: am I forced to abuse of Thread.pass in (every heavy) threads
or may I just assume the ruby interpreter will commute threads itself?

Yes, ruby will handle thread scheduling.

Another question:
Is Ruby multithreading blocked by system calls?

Like for example when calling system("command line").

Hmm, good question. I assume yes, but let's let someone who knows
better than me answer this one...

James Edward Gray II

 

[Michael Neumann]

Yes, ruby will handle thread scheduling.



Hmm, good question. I assume yes, but let's let someone who knows
better than me answer this one...

Yes:

Thread.new {
loop do
sleep 1
p "."
end
}

system("sleep 10000")

And for IO operations, this is true, too. Ruby does not block on
read/write as it internally uses select.

Regards,

Michael

 

[Lionel Thiry]

Yes:

Thread.new {
loop do
sleep 1
p "."
end
}

system("sleep 10000")

And for IO operations, this is true, too. Ruby does not block on
read/write as it internally uses select.

Regards,

Michael

Thanks all,
Lionel

 

[Eric Hodel]

Yes:

Thread.new {
loop do
sleep 1
p "."
end
}

system("sleep 10000")

And for IO operations, this is true, too. Ruby does not block on
read/write as it internally uses select.

No, system does not block other ruby threads.

$ cat x.rb
STDOUT.sync = true

Thread.new {
loop do
sleep 1
puts Time.now
end
}

system("sleep 10")

$ ruby -v x.rb
ruby 1.8.2 (2004-11-06) [powerpc-darwin7.6.0]
Fri Dec 03 09:57:47 PST 2004
Fri Dec 03 09:57:48 PST 2004
Fri Dec 03 09:57:49 PST 2004
Fri Dec 03 09:57:50 PST 2004
Fri Dec 03 09:57:51 PST 2004
Fri Dec 03 09:57:52 PST 2004
Fri Dec 03 09:57:53 PST 2004
Fri Dec 03 09:57:54 PST 2004
Fri Dec 03 09:57:55 PST 2004
$

 

[Lionel Thiry]

No, system does not block other ruby threads.
Thanks for the remark... I was a bit confused about my interpretation of
the answer, and I could not test system("sleep 10000") on my windows2k
to see how it works.

$ cat x.rb
STDOUT.sync = true

I didn't know that stuff!
It's interesting, where is that documented?

Thread.new {
loop do
sleep 1
puts Time.now
end
}

system("sleep 10")

$ ruby -v x.rb
ruby 1.8.2 (2004-11-06) [powerpc-darwin7.6.0]
Fri Dec 03 09:57:47 PST 2004
Fri Dec 03 09:57:48 PST 2004
Fri Dec 03 09:57:49 PST 2004
Fri Dec 03 09:57:50 PST 2004
Fri Dec 03 09:57:51 PST 2004
Fri Dec 03 09:57:52 PST 2004
Fri Dec 03 09:57:53 PST 2004
Fri Dec 03 09:57:54 PST 2004
Fri Dec 03 09:57:55 PST 2004
$

Thanks for the help,
Lionel Thiry

 

[Eric Hodel]

Thanks for the remark... I was a bit confused about my interpretation
of the answer, and I could not test system("sleep 10000") on my
windows2k to see how it works.

Maybe only on (some) windows builds it blocks? I no longer have a
windows machine handy to test these things on.

I didn't know that stuff!
It's interesting, where is that documented?

ri has it:

$ ri IO#sync
---------------------------------------------------------------- IO#sync
ios.sync => true or false
------------------------------------------------------------------------
Returns the current ``sync mode'' of _ios_. When sync mode is true,
all output is immediately flushed to the underlying operating
system and is not buffered by Ruby internally. See also +IO#fsync+.

f = File.new("testfile")
f.sync #=> false
$ ri IO#sync=
--------------------------------------------------------------- IO#sync=
ios.sync = boolean => boolean
------------------------------------------------------------------------
Sets the ``sync mode'' to +true+ or +false+. When sync mode is
true, all output is immediately flushed to the underlying operating
system and is not buffered internally. Returns the new state. See
also +IO#fsync+.

f = File.new("testfile")
f.sync = true

_(produces no output)_

 

[Lionel Thiry]

Maybe only on (some) windows builds it blocks? I no longer have a
windows machine handy to test these things on.

I haven't correcly explained. On my w2k, the sleep command simply
doesn't exists, then I couldn't test that ruby code. And I have no clue
about a substitute.

ri has it:

$ ri IO#sync

Oh yes! I forgot STDOUT was simply an IO object.
But why do we need it here?

Lionle Thiry

 

[Eric Hodel]

I haven't correcly explained. On my w2k, the sleep command simply
doesn't exists, then I couldn't test that ruby code. And I have no
clue about a substitute.

Yes, I know.

Oh yes! I forgot STDOUT was simply an IO object.
But why do we need it here?

To be explicit and to behave as expected when you run it on a machine
with sleep. Without it, the OS may buffer the printing, and flush when
the program exits (all 10 lines at once). This would give the
appearance that system() blocked the Ruby thread.