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Meothuru <nomail@nomail> wrote:
> A normal user have only a limited bandwith of CPU-power and this is far
> away from 100% CPU power.
Far away? Not really.
If nothing CPU-intensive is running at the same time, a CPU-intensive
program (such as POV-Ray) will get almost 100% (usually from 99% upwards).
The OS doesn't need almost any CPU at all for task switching, and if
there isn't anything else using the CPU heavily, then there's nothing
which would require it.
> Because a program/user wich gets realy 100% of
> the CPU power would block the computer for all other programs/users.
He said "nearly 100%". That is, not exactly 100%, but a bit lower,
like 99.5%, which by all practical purposes is the same thing.
> And this can not be allowed in a Multiuser-System.
I think you misunderstand. POV-Ray takes all the CPU time which is
unused. If nothing else is using the CPU, then it takes all of it.
That doesn't mean that if another CPU-intensive program is started
it would not get its share.
> You can verify this very simple. Go to the "root-mode" and start
> provray with the highest possible "nice value" of the privileged mode.
> In this mode povray gets *much more* CPU-power than a normal user can
> ever get....
Much more? I would need to see some evidence before I believe that.
--
- Warp
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On Mon, 14 Aug 2006 09:29:51 -0400, Warp wrote:
> I think you misunderstand. POV-Ray takes all the CPU time which is
> unused. If nothing else is using the CPU, then it takes all of it.
> That doesn't mean that if another CPU-intensive program is started
> it would not get its share.
I think that would depend on the comparitive niceness levels, though,
wouldn't it? POV-Ray doesn't yield entirely to another process that wants
CPU - they participate in a timesharing system.
If I start a render in POV-Ray and then launch xmoto (a fairly intensive
game), I don't get the same degree of smoothness in running xmoto with
POV-Ray running as I do with it running. I can either suspend POV-Ray
entirely (ctrl-Z in POV-Ray's term window), or I can change the niceness
levels of either (or both) programs. I still get some jerkiness in the
graphics in the game, but it's not as pronounced.
I've never observed POV-Ray automatically yielding processor to whatever
other applications are running on the system or tuning it's
niceness/priority level in the system. If it does that, great, but I'd
love to know how to turn it on because it doesn't seem to be a default
behaviour; it seems to behave like any other application running on the
system.
Jim
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> I think that would depend on the comparitive niceness levels, though,
> wouldn't it?
Of course.
> I still get some jerkiness in the
> graphics in the game, but it's not as pronounced.
If you give the lowest priority to your POV-Ray job (+20), you should
get nearly the same effect as suspending it. But not quite, as it would still
get maybe 1-2% of the resources on average.
> I've never observed POV-Ray automatically yielding processor to whatever
> other applications are running on the system or tuning it's
> niceness/priority level in the system.
AFAIK only the OS - say the user on top of it - can do that in a Unix environment.
(Honestly I never looked at this possibility.)
- NC
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On Mon, 14 Aug 2006 19:26:56 +0200, Nicolas Calimet wrote:
>> I still get some jerkiness in the
>> graphics in the game, but it's not as pronounced.
>
> If you give the lowest priority to your POV-Ray job (+20), you should
> get nearly the same effect as suspending it. But not quite, as it would
> still get maybe 1-2% of the resources on average.
Sounds about right. Doesn't the niceness level adjust the timeslicing
used, or is that controlled by something else?
> AFAIK only the OS - say the user on top of it - can do that in a Unix
> environment.
That's my understanding as well - and even then, I think it depends on
which part of the OS we're talking about as well. I have seen user
processes run away with a Linux kernel to the point the machines becomes
nonresponsive on the network (granted, that's probably still too far away
from the kernel, since it's services not responding that would be the
indicator of this behaviour.)
Jim
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> Doesn't the niceness level adjust the timeslicing
> used, or is that controlled by something else?
Best is to ask Google :-)
http://www.samspublishing.com/articles/article.asp?p=101760&rl=1
> I have seen user
> processes run away with a Linux kernel to the point the machines becomes
> nonresponsive on the network
I've faced litterally frozen desktops mostly when an user app started to
swap like hell because of too high a memory demand.
- NC
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On Tue, 15 Aug 2006 02:23:20 +0200, Nicolas Calimet wrote:
>> Doesn't the niceness level adjust the timeslicing
>> used, or is that controlled by something else?
>
> Best is to ask Google :-)
>
> http://www.samspublishing.com/articles/article.asp?p=101760&rl=1
<G> Or I could peruse the kernel source, at that. :-)
>> I have seen user
>> processes run away with a Linux kernel to the point the machines becomes
>> nonresponsive on the network
>
> I've faced litterally frozen desktops mostly when an user app started to
> swap like hell because of too high a memory demand.
Yep, I see that on occasion here as well - usually something like
beagled-helper most recently - I need to file a bug on that, but I swap so
infrequently that I thought the monitor applet was broken until that thing
started burning memory up.
Jim
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Jim Henderson <nos### [at] nospam com> wrote:
> I think that would depend on the comparitive niceness levels, though,
> wouldn't it?
If two cpu-intensive processes have the same nice level, then the OS
will share the CPU among them about equally.
Naturally if one of the processes has a higher nice value then the OS
will give less CPU to it and more to the other (I'm not exactly sure
about the formula the OS uses for that; could even depend on the OS;
it would be interesting to know what the linux kernel does).
However, I got the impression from the original claim that if the
OS would run POV-Ray at maximum efficiency (ie. giving it almost 100%
of CPU time) then it would somehow be difficult for anything else to
do anything, and that everything else would go really slow. I got the
impression that he thought that if POV-Ray has (almost) 100% of CPU,
it would have something like "hijacked" the entire computer to itself
and that it would be difficult to get the resources back.
But of course that's not the case in Unix systems (nor in Windows).
The task scheduler has full control of the machine and nothing can go
over it. It will always schedule tasks at regular intervals (I think
that in a typical linux OS it does so each millisecond) and there's
nothing a program can do about it. This means in practice that the
task scheduler can for example completely stop a program from running
if it wants (and it doesn't matter if that program was using 99.9% of
CPU or whatever). The task scheduler has complete control. It cannot
be "hijacked" by any program in any way.
--
- Warp
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you all run on Linux. I own a pentium 4 dual core Acer and currently running
3.61 on XP. Using 3.7 renders slower then the 3.61 version.
- Does it make a difference in speed if I use the Windows version (on XP) or
if I run it on Linux ?
- How can I check on Windows XP if the second core is indeed used ?
thanx
Adrie
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bagger <adr### [at] asmlcom> wrote:
> - How can I check on Windows XP if the second core is indeed used ?
Just open the task manager (ctrl-alt-del) and go to the processor tab
(or whatever it was called).
--
- Warp
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Warp <war### [at] tagpovrayorg> wrote:
> bagger <adr### [at] asmlcom> wrote:
> > - How can I check on Windows XP if the second core is indeed used ?
>
> Just open the task manager (ctrl-alt-del) and go to the processor tab
> (or whatever it was called).
>
> --
> - Warp
that only gives the percentage of CPU used. Does a 100% garantuee me that
both cores are used ? (by the way does every core have a seperate FPU ?)
Does anyone know if the Linux variant is faster then the Windows XP variant
?
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