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after --update @world all cores now report same load
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mjbjr
Apprentice
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Joined: 02 Mar 2003
Posts: 233

PostPosted: Thu Aug 04, 2016 10:09 am    Post subject: after --update @world all cores now report same load Reply with quote

For years I've been using 'gkrellm' to visually monitor the system hardware.
The system has an Intel quad core that gets virtualized to eight cores.
gkrellm shows graphs for all eight cores.

Previous to a recent 'emerge --update --newuse --deep --with-bdeps=y @world',
the cores' graphs were all quite different for any one task. Small tasks might
show a couple of thin spikes in the first two or three cores' graphs with nothing
at all or at least substantially less spikes and noise for any of the other cores.

A medium sized task would create more and larger spikes with more floor noise,
and affect more cores.

With larger projects, compiling the kernel or chromium, etc., causing the cores'
noise levels to be quite high with some spikes higher still, across ALL cores more
or less equally.

Now, after the --update @world, a simple task produces one or two spikes and no
noise floor and is shown *identically* across all eight cores' charts, when it should only
occupy a core or two.

So, basically, now all cores show the same graphs regardless of the size of the current task.
And the graphs seem to all be showing higher levels generally.

It's unusual for this machine.

The --update @world did not include a kernel (4.1.12) upgrade.

An upgrade for 'gkrellm' made no difference in the new behavior.
'htop' was reporting the same as gkrellm, approximately equal loads across all cores.


To summarize, if gkrellm and htop are correct, since the --update @world update
the same old tasks are causing the cores to do more work, which gets distributed
across more cores than ever before, regardless the size of the task.


Anyone have any ideas on why this change might have occurred?

thanks

-------------------
machine info

# uname -a
Linux localhost 4.1.12-gentoo #13 SMP Sun Jan 3 11:56:12 PST 2016 x86_64 Intel(R) Core(TM) i7-4820K CPU @ 3.70GHz GenuineIntel GNU/Linux

with 32GB of memory.
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eccerr0r
Watchman
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Joined: 01 Jul 2004
Posts: 7130
Location: almost Mile High in the USA

PostPosted: Thu Aug 04, 2016 11:47 pm    Post subject: Reply with quote

Most likely, a kernel change. Or if the program is using ninja instead of make. Or you changed your -j and -l options to make.

Ideally all 8 virtual cores are fully utilized, it would mean your machine is fully used for the fastest building of your software. Usually that is the case on my i7. Anything less may still be completely used but you can't be for certain. Hopefully the scheduler picks out cores over threads, that depends on you have those kernel support options enabled.
_________________
Intel Core i7 2700K@ 4.1GHz/HD3000 graphics/8GB DDR3/180GB SSD
What am I supposed watching?
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mjbjr
Apprentice
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Joined: 02 Mar 2003
Posts: 233

PostPosted: Fri Aug 05, 2016 2:31 am    Post subject: Reply with quote

eccerr0r wrote:
Most likely, a kernel change. Or if the program is using ninja instead of make. Or you changed your -j and -l options to make.

Ideally all 8 virtual cores are fully utilized, it would mean your machine is fully used for the fastest building of your software. Usually that is the case on my i7. Anything less may still be completely used but you can't be for certain. Hopefully the scheduler picks out cores over threads, that depends on you have those kernel support options enabled.


Thank you for the response.

Nope, no kernel change, no make.conf changes.
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