Dual Processor management: isolating CPU for a certain process

[xtknight]

Too bad the performance of VT is worse in a lot of cases :/ http://www.vmware.com/pdf/asplos235_adams.pdf

 

[Nothinman]

Because of the way each of the 2 threads is running with just over a 50% duty cycle, assuming nothing else is using the 2 cores, Speedstep, Power Now, or Cool n' Quiet will slow down the CPU! But if you set the affinity, it will run at full clock speed.

Then it's a problem with how quickly Cool n' Quiet decides to turn the CPUs down not the OS scheduler or the app.

 

[drag]

Originally posted by: Nothinman

Because of the way each of the 2 threads is running with just over a 50% duty cycle, assuming nothing else is using the 2 cores, Speedstep, Power Now, or Cool n' Quiet will slow down the CPU! But if you set the affinity, it will run at full clock speed.

Then it's a problem with how quickly Cool n' Quiet decides to turn the CPUs down not the OS scheduler or the app.

Well Cooln'Quiet is a ACPI thing, right? So even then it is still a OS issue of a different sort. But ya, disabling Cool n'Quiet is the solution to this problem, not so much setting afinity.

 

[Smilin]

Originally posted by: Rilex

Originally posted by: Smilin
This is most obvious during guest OS setup where VM additions are not present - setup runs like crap and takes forever. 🙁

That is what VT/Pacifica are for 😉

Uh, no. To enable VT support you have to have the VM additions running as well 🙂

Actually you have to have the *latest* VM additions for VT. We got new Dual core, 4GBram, 500GBhdd machines to replace our secondary boxes for everyone here at work. A lot of us went to Virtual Server R2 at the same time we got these boxes but still had the older VM additions on. Performance jumps after you update the VM additions in the guests.

 

[Nothinman]

Well Cooln'Quiet is a ACPI thing, right? So even then it is still a OS issue of a different sort. But ya, disabling Cool n'Quiet is the solution to this problem, not so much setting afinity.

I thought it was a userland daemon (like powernowd) and if so how it does the transitions is irrelevant since it's the daemon determining when to change CPU speeds.

 

[ebaycj]

Originally posted by: Nothinman

Well Cooln'Quiet is a ACPI thing, right? So even then it is still a OS issue of a different sort. But ya, disabling Cool n'Quiet is the solution to this problem, not so much setting afinity.

I thought it was a userland daemon (like powernowd) and if so how it does the transitions is irrelevant since it's the daemon determining when to change CPU speeds.

if it is a userland daemon, it's probably configurable.

 

[Smilin]

Originally posted by: Nothinman

Well Cooln'Quiet is a ACPI thing, right? So even then it is still a OS issue of a different sort. But ya, disabling Cool n'Quiet is the solution to this problem, not so much setting afinity.

I thought it was a userland daemon (like powernowd) and if so how it does the transitions is irrelevant since it's the daemon determining when to change CPU speeds.

kernel driver/service in Windows if I remember right. Don't quote me.

 

[Nothinman]

kernel driver/service in Windows if I remember right. Don't quote me.

Even so it's not ACPI, hardware or Windows determining when to scale back the CPU, so it's still AMD/Cool n' Quiet's problem.