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Old 2006-10-16, 12:02   #1
JuanTutors
 
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Default Feature request: Prime95 priority higher than 10

Now that dual core machines are out, I was wondering if we can make prime95 have priority higher than 10. With my old computer, running at priority 10 wasn't possible because just stopping prime95 would take 15 minutes. But with my new computer I can run one copy of prime95 at priority 10, the other at priority 1-8, and have no noticable performance hit.
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Old 2006-10-16, 18:26   #2
Ethan Hansen
 
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Priority level 10 corresponds to the Windows ABOVE_NORMAL_PRIORITY_CLASS. Running at a higher priority level can cause problems. If a process runs at the next step up, HIGH_PRIORITY_CLASS, all other user threads on that CPU will never get processor time. That can cause problems if the high priority process runs for extended times. Typically the high priority class is used for short duration threads whose response to external events that are time-critical. Running Prime95 at HIGH_PRIORITY is going to be of only marginal benefit - on the order of a few clocks per billion. It is quite likely, however, to cause problems with other applications.

The highest priority option is REALTIME_PRIORITY_CLASS. Applications running continuously at this level are really something to avoid. All system management threads, including keyboard and mouse input, disk flushing, etc. are put on hold. Realtime priority is useful for direct communications with hardware, as long as the time involved is brief or *nothing* else is expected to run on the system.
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Old 2006-10-16, 22:59   #3
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Quote:
Originally Posted by dominicanpapi82 View Post
I can run one copy of prime95 at priority 10, the other at priority 1-8, and have no noticable performance hit.
According to what Ethan wrote, there's actually a large probability of a noticeable performance hit. Have you actually tried using priority 9 for a long period of time and experimenting to see what effect that has?

Personally, I recommend just leaving it at priority 0.
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Old 2006-10-17, 15:25   #4
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No matter what the priority, the work still needs to be done.

If I run a word processor I want it to react fast to help improve my productivity. There seems little sense in forcing myself to wait while a macro runs at lower priority than P95, because, no matter what priority it has, the macro's work also needs to be done.

Conclusion: You gain nothing by elevating the P95 priority and waste more time from your own life.
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Old 2006-10-18, 04:21   #5
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Quote:
Originally Posted by cheesehead View Post
Have you actually tried using priority 9 for a long period of time and experimenting to see what effect that has?
For my dual core, I always have one copy running at priority 10. While I'm on the computer, I have the second copy run at priority just 1. With one at 10 and one at 1, there's no performance hit AT ALL. In fact I don't notice a performance hit until the second copy is at priority 9 or 10. I keep it at priority 1 while I'm on the computer because I don't know which processes will be slowed in any way.

I also tried going to the processes list and right clicking and running the second copy of prime95 at real time priority, with the first copy at priority 1. I don't know if this actually did anything, but there is still no noticable performance hit.

Last fiddled with by JuanTutors on 2006-10-18 at 04:22
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Old 2006-10-18, 07:41   #6
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Is there any performance gain from running Prime95 with increased priority? If not, then why bother?
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Old 2006-10-18, 11:58   #7
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Quote:
Originally Posted by dominicanpapi82
I always have one copy running at priority 10. While I'm on the computer, I have the second copy run at priority just 1
It would seem you don't run any multi-threaded apps. So basically you are dedicating one core to P95 and forcing all other apps to run on the other core. For sure a simple word processing program probably won't use multi-threads to run a macro so you don't notice any performance hit because the processor that is being shared has P95 at priority 1. But, for other users that use different (multi-threaded) apps, it is important not to mess with their priorities else they might get annoyed with P95 for "stealing" one core.
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Old 2006-10-19, 04:20   #8
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Quote:
Originally Posted by Cruelty View Post
Is there any performance gain from running Prime95 with increased priority? If not, then why bother?
Ideally it's supposed to be no, but for me it's always been a very definite yes.

Quote:
Originally Posted by retina View Post
It would seem you don't run any multi-threaded apps.
Yes that's pretty true.

Quote:
Originally Posted by retina View Post
So basically you are dedicating one core to P95 and forcing all other apps to run on the other core. For sure a simple word processing program probably won't use multi-threads to run a macro so you don't notice any performance hit because the processor that is being shared has P95 at priority 1. But, for other users that use different (multi-threaded) apps, it is important not to mess with their priorities else they might get annoyed with P95 for "stealing" one core.
While on the computer, I keep one copy running at priority 1. I can't imagine why I'd see a performance hit this way, considering when anyone is on a single core computer with prime95 running at priority 1 they don't notice a performance hit. (Unless they do and it's minimal enough that they don't mention it.) I figure any performance hit they get would be just about the same as they would take on a dual core running at least one copy at priority 1.

Last fiddled with by JuanTutors on 2006-10-19 at 04:44
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Old 2006-10-19, 07:11   #9
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Quote:
Originally Posted by dominicanpapi82 View Post
Ideally it's supposed to be no, but for me it's always been a very definite yes.
How much % do you actually gain?
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Old 2006-10-19, 22:18   #10
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You may see a gain in P95 throughput on one processor, as all work is being sent to the other. If you run multiple applications or any apps that are multi-threaded, however, you lose all benefit of having the second processor. Unless you have some other background program devouring processor cycles, you shouldn't see much difference in Prime95 times.
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Old 2006-10-20, 14:36   #11
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Quote:
Originally Posted by Cruelty View Post
How much % do you actually gain?
For my single core machine, if I'm not on the computer then about 5%. Actually I run it at priority 8 when I AM on it, and that gives me between a 15% and 35% improvement. I don't know if priority 8 is generally a good thing for single core machines, judging from what people have said above

For my dual core machine, if I run one copy at priority 10, then I get about 5% improvement while off it, and 15 to 35% improvement while on it. I noticed my second copy, which will run at priority 1 while on it, doesn't slow down NEARLY twice as much, so the speed gain is actually pretty accurate.
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