CPU Usage

[rueyloon]

Question

I'm running FCPX export on a 12 core and I see the top 2 processes as

1) Transcodertool - around 600% CPU
2) FCPX - around 300% CPU

Does it mean 6 cores are fully utilised ? (overlapping)
or
Does it mean 9-10 cores are fully utilised ? (non overlapping)


What will happen if this process is run on a 10 core ? or 8 core ?


Just still trying to understand the core vs clock speed thingy.

rgs
rueyloon

 

[jdphoto]

Question

I'm running FCPX export on a 12 core and I see the top 2 processes as

1) Transcodertool - around 600% CPU
2) FCPX - around 300% CPU

Does it mean 6 cores are fully utilised ? (overlapping)
or
Does it mean 9-10 cores are fully utilised ? (non overlapping)


What will happen if this process is run on a 10 core ? or 8 core ?


Just still trying to understand the core vs clock speed thingy.

rgs
rueyloon

If I'm not mistaken you are using 9-10 cores. Things shouldn't "overlap" unless you've run out of cores. What does it show for your overall CPU usage? Is the user + system around 75%?

 

[rueyloon]

So if this process is running on a 10 core processor, will it still use the cores in the same way ? or will it only run to say a max of 8 because 2 is always reserved for OS and other background stuff ?

If I'm not mistaken you are using 9-10 cores. Things shouldn't "overlap" unless you've run out of cores. What does it show for your overall CPU usage? Is the user + system around 75%?

 

[AidenShaw]

There are no reservations

So if this process is running on a 10 core processor, will it still use the cores in the same way ? or will it only run to say a max of 8 because 2 is always reserved for OS and other background stuff ?

There is no concept of "reserving cores" in any modern mainstream OS. (And even though much of OSX is based on 1970's UNIX systems, it counts as "modern" due to the continual adoption of improved code.)

The scheduler dynamically assigns computable threads to idle cores -- it will never leave a core idle if there are threads ready to compute.

If a particular thread (say an "OS thread") is of higher priority than other threads waiting for a core - then that thread will be scheduled before "normal" or "background" threads.

So - important threads will get preference, but the idea of a static "these cores are for the OS" allocation is simply not true.

 

[jdphoto]

There is no concept of "reserving cores" in any modern mainstream OS. (And even though much of OSX is based on 1970's UNIX systems, it counts as "modern" due to the continual adoption of improved code.)

The scheduler dynamically assigns computable threads to idle cores -- it will never leave a core idle if there are threads ready to compute.

If a particular thread (say an "OS thread") is of higher priority than other threads waiting for a core - then that thread will be scheduled before "normal" or "background" threads.

So - important threads will get preference, but the idea of a static "these cores are for the OS" allocation is simply not true.

Exactly what he said. Threads are allocated as needed, nothing is reserved.

 

[AidenShaw]

clarification

There is no concept of "reserving cores" in any modern mainstream OS. (And even though much of OSX is based on 1970's UNIX systems, it counts as "modern" due to the continual adoption of improved code.)

Actually, "hard affinity" is a way of reserving cores - but it is seldom used except in very specific circumstances (such as when you know that certain cores share levels of the cache hierarchy or NUMA nodes, and you want to make sure that some sets of threads share the same cache or NUMA).

In general, manually mucking around with affinity will hurt performance - you'll have idle cores while threads are waiting for cores.

 

[rueyloon]

Hi, thanks for all the answers, but is the method I used a good way to estimate optimal system configuration ? Like it seems like 10 cores is the optimum configuration for THAT process that I've shown. Or the whole thing will be jumbled up again when the computer sees a different number of cores for it to use ?

rgs
rueyloon