CPU usage for handbrake

[TomLopez]

Hi there,

I have received one week ago my new MBP 2011 15" (2,2Ghz, hi-res with 128Go SSD) to replace my MBP 2010 (i7 2,66GHz). I'm fully satisfied with it :
* no heat: 32° idle on Intel, 38° on ATI and about 50° in all the day use with the ATI card
* very fast in multitasks, video/audio editing, etc...
* the SSD is very appreciable and although it is not as fast as SATA 3 ones, I guess the difference is hardly noticeable. I even get close scores for reboot, standby, etc... as if Apple SSD are optimized for MAC OS.

I have just one concern with it: with handbrake for video encoding, the Handbrake process is using 550-650% of CPU instead of something closer to 800%. Do you have an idea?

 

[bozz2006]

Do you have other applications running? If so, especially intensive applications like Logic or Final Cut or any of the Adobe applications, your system doesn't want to completely starve them for resources so it won't use ~800% cpu. Check handbrake with all other applications closed and see if that has an effect. Another thing is that some of the settings in HB just don't squeeze every drop of cpu. Mess with the settings a bit too and see if that has an effect.

 

[Transporteur]

Handbrake doesn't utilise more than 70 to 80% CPU cycles.

On my system, about 1000 to 1200% is the maximum HB takes. I simply run two instances to max out the machine.

 

[TomLopez]

Thanks for your replies,
In fact I have other applications running in the meantime but they don't need ressources. Basically I have Handbrake @ 550% and Idle process @ 250%.

I am asking because on my last year MBP, Handbrake was systematically using 390% (so the max the machine can provide)

 

[gwerhart0800]

Could it also be related to hyperthreading? The hyperthreading requires that if the primary thread stalls because it is waiting for something (like a fetch from memory), then a second thread that is waiting for execution can use the execution units until the stall state has been satisfied. Handbrake is shoving a ton of data through the CPU and I would expected frequent stalls waiting for data to be read. If all threads available to a core are stalled, then that core is idle for a time. The stall rate will be related to the size of the cache and the speed at which the data can be read from the physical medium. At some point, you can increase the number of execution threads to the point that you can out strip the ability to read the data from disk fast enough to keep them all satisfied. I can't claim for sure that this is the case ... especially since you have an SSD ... assuming that the video being transcoded is stored on and being written back to the SSD.)

 

[Detrius]

I've not tried it on one of these machines, but eventually, you're going to run into a different bottleneck: the optical drive. It's theoretically possible that's what's going on, too.

 

[TomLopez]

I've not tried it on one of these machines, but eventually, you're going to run into a different bottleneck: the optical drive. It's theoretically possible that's what's going on, too.

In this case I'm encoding a video stored on my SSD not a DVD in the Superdrive

gwerhart0800 you highlight a good point but an avi file of 700Mo get transcoded in about 15 min so it is about 1Mb/s to read/write. I assume this is note a problem even with a ''standard'' HD.

I will reboot my laptop and check how it performs with only handbrake running

 

[sr55]

This is normal. It'll use what it can, but usage will vary depending on the source content and settings used. Anything from 1 to 12 cores used is typical. So pretty large range there.

You don't tend to see much benefit beyond 8-12 Cores at the moment.

 

[Transporteur]

I will reboot my laptop and check how it performs with only handbrake running

There won't be any difference.
Again, on machines with high amount of cores (which includes HT cores), CPU utilisation won't go beyond 70 to 80%. You can read about that on the Handbrake forums.

Quote from Barefeats:
"Notice the 12-core Mac Pro is NOT twice as fast as the 6-core Mac Pro. That's because HandBrake does not use all available cores. Using Activity Monitor, I observed a maximum cpu load of 1000% (or 10 cores). Most of the time during the conversion, it was at 500% cpu load (or 5 cores). Since the 6-core Mac Pro is capable of 12 virtual cores, it's easy to understand why it's only slightly slower than the 12-core (24 virtual) Mac Pro."

 

[TomLopez]

There won't be any difference.
Again, on machines with high amount of cores (which includes HT cores), CPU utilisation won't go beyond 70 to 80%. You can read about that on the Handbrake forums.

Quote from Barefeats:
"Notice the 12-core Mac Pro is NOT twice as fast as the 6-core Mac Pro. That's because HandBrake does not use all available cores. Using Activity Monitor, I observed a maximum cpu load of 1000% (or 10 cores). Most of the time during the conversion, it was at 500% cpu load (or 5 cores). Since the 6-core Mac Pro is capable of 12 virtual cores, it's easy to understand why it's only slightly slower than the 12-core (24 virtual) Mac Pro."

Hmm it seems it's better since the reboot (uptime was 7 days):

I have also no heat issue at all as my max temps are about 85° (the file on the screenshot is the third that was transcoded). Even the fans are not running at max rpm