cmp(1) has a bottleneck, but where?

Garrett Cooper yanegomi at
Tue Jan 3 01:38:03 UTC 2012

On Mon, Jan 2, 2012 at 5:29 PM, Dieter BSD <dieterbsd at> wrote:
>>> Task: cp(1) a several-GB file from one drive to another,
>>> then run cmp(1) to verify.  Cp runs as expected, but
>>> cmp runs slower than expected.  Neither the disks
>>> nor the cpu is maxed out.  Local drives, no network
>>> involved.  Machine is otherwise idle.
>>    1. How are you running cmp?
>>    2. Why do you claim cmp is the bottleneck? Is it spinning the CPU?
> cmp big_file /other_disk/big_file
> Cmp is running slower than it should.  It isn't cpu bound ( 67.5%Idle )
> but it isn't disk bound either.  Seems like it should be one or the
> other.

    What gets output on the console when you do CTRL-T?

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