slow down dd - how?

[Greg Larkin]

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David Kelly wrote:
> On Thu, Jul 08, 2010 at 06:44:38PM +0200, Roland Smith wrote:
>> On Thu, Jul 08, 2010 at 05:50:52PM +0200, Jozsi Avadkan wrote:
>>> How can I slow down dd?
>> Play with the block size parameter (bs). Smaller block sizes means more
>> reads. The default is 512 bytes, which is very small.
>>  
>>> I don't want to slow down the pc, when generating a big file [~40
>>> GByte].
> 
> I don't think Jozsi wants to burn more CPU cycles, just slow the
> process. Perhaps to attract less attention? Or interfere less with other
> processes.
> 
> Nice(1) is a good start but rtprio(1) is probably where he should look.
> 
> Also consider that writing a program of your own to serve as a slow pipe
> shouldn't be very hard. Think it would be a good exercise as an
> introduction to Unix programming. Simply copy stdin to stdout with a
> usleep(3) between. Pipe dd through your slowpipe program.
> 
> Someone else has probably written a slow pipe. I haven't looked.
> 

Indeed someone has, and I ported it a few months back:
http://www.freshports.org/sysutils/pmt.  Check the "throttle" subcommand.

I also use idprio(1)
(http://www.freebsd.org/cgi/man.cgi?query=idprio&sourceid=opensearch) to
schedule processes that I don't want interfering with the rest of the
system.

Hope that helps,
Greg
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Greg Larkin

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