[cgl_discussion] Re: device enumeration

Steven Dake sdake at mvista.com
Fri Feb 7 10:58:30 PST 2003


Perez-Gonzalez, Inaky wrote:

>>Performance is _so_ critical here, because if the removal 
>>operation is 
>>fast enough, there is no phsyical way to remove the device from the 
>>slot/bus/whatever before the OS has removed the device from the 
>>operating system data structures.
>>    
>>
>
>Then change /sbin/hotplug ... its main benefit is your are NOT constrained
>by a model. Make it pass, real fast, it's parameters to a daemon that is
>already running via the fastest method you can devise [eg: shared memory].
>  
>
There is no way to do this, since /sbin/hotplug is executed each time 
and cannot be run as a daemon.

>Then have a process mmap & lock a binary /sbin/hotplug to have it
>permanently cached and avoid the startup overhead. 
>
>I bet you can beat 20ms and whatever, although I don't think an operator
>will be able to tell the difference between 20ms and 1s - it is going to
>take so much time to shut the system down that those 20ms are going to be
>meaningless ...
>  
>
the 20ms is mostly for the OS to shut down its internal data structures. 
 /sbin/hotplug adds approx 25 msec to the entire operation.  1 second 
may be ok for shutting down a typical windows server system, but a cpu 
or disk blade that can be removed (such as compact pci or advanced tca) 
needs faster performance.

Thanks
-steve

>Inaky Perez-Gonzalez -- Not speaking for Intel - opinions are my own [or my
>fault]
>
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