Question on routing hotplug events to open-ipmi interface

Question on routing hotplug events to open-ipmi interface

[Krishna Pidamale]

My system has plenty of hotpluggable SATA drives, and system runs either SLES or RHEL (older and newer distributions). Through /etc/hotplug/scsi.agent I could verify all hotplug add and remove events with DEVPATH. I would like to pass these event info to OPEN-IPMI interface, which means I will write a small C 
program to do this. Can I execute this program from scsi.agent? I am concerned about performance hit due to "n" instances of this executable. Since drives can be added/removed several times, it could add up many events. 

Is this /sbin/hotplug utility meant for such operation? Any suggestions to avoid performance degradation? How can udev help here? Where can I find additional information? 

-Krishna









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Re: Question on routing hotplug events to open-ipmi interface

[Kay Sievers]

On Thu, 2006-08-17 at 23:07 -0700, Krishna Pidamale wrote:
> My system has plenty of hotpluggable SATA drives, and system runs either SLES or RHEL (older and newer distributions). Through /etc/hotplug/scsi.agent I could verify all hotplug add and remove events with DEVPATH. I would like to pass these event info to OPEN-IPMI interface, which means I will write a small C 
> program to do this. Can I execute this program from scsi.agent? I am concerned about performance hit due to "n" instances of this executable. Since drives can be added/removed several times, it could add up many events. 
> 
> Is this /sbin/hotplug utility meant for such operation? Any suggestions to avoid performance degradation? How can udev help here? Where can I find additional information? 

Depends on the size of you box. The only sane thing you can do
with /sbin/hotplug is to disable it. :) It's simply a fork-bomb that
kills your box when you generate a lot of events.

Old SLES kernels have kernel code, to limit the number of parallel
running /sbin/hotplug processes, standard kernels may create
out-of-memory situations on big boxes.

Newer udev versions connect with the udevd daemon to the kernel over a
netlink socket and don't exec() a binary for every event. Also the
created system load created by event handlers is limited by udevd.

There is no way to work with /sbin/hotplug in a performance critical
setup or on big boxes. Use a newer distro release with a recent kernel
+udev, if you expect a lot of events. Everything else may work, but if
your setup creates more than the usual number of events you may not even
be able to bootup with /sbin/hotplug in use.

Thanks,
Kay


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Re: Question on routing hotplug events to open-ipmi interface

[Krishna Pidamale]

THANK YOU  Kay  for your input,  let me dig udevd and more.

-Krishna


Sievers wrote:

>On Thu, 2006-08-17 at 23:07 -0700, Krishna Pidamale wrote:
>  
>
>>My system has plenty of hotpluggable SATA drives, and system runs either SLES or RHEL (older and newer distributions). Through /etc/hotplug/scsi.agent I could verify all hotplug add and remove events with DEVPATH. I would like to pass these event info to OPEN-IPMI interface, which means I will write a small C 
>>program to do this. Can I execute this program from scsi.agent? I am concerned about performance hit due to "n" instances of this executable. Since drives can be added/removed several times, it could add up many events. 
>>
>>Is this /sbin/hotplug utility meant for such operation? Any suggestions to avoid performance degradation? How can udev help here? Where can I find additional information? 
>>    
>>
>
>Depends on the size of you box. The only sane thing you can do
>with /sbin/hotplug is to disable it. :) It's simply a fork-bomb that
>kills your box when you generate a lot of events.
>
>Old SLES kernels have kernel code, to limit the number of parallel
>running /sbin/hotplug processes, standard kernels may create
>out-of-memory situations on big boxes.
>
>Newer udev versions connect with the udevd daemon to the kernel over a
>netlink socket and don't exec() a binary for every event. Also the
>created system load created by event handlers is limited by udevd.
>
>There is no way to work with /sbin/hotplug in a performance critical
>setup or on big boxes. Use a newer distro release with a recent kernel
>+udev, if you expect a lot of events. Everything else may work, but if
>your setup creates more than the usual number of events you may not even
>be able to bootup with /sbin/hotplug in use.
>
>Thanks,
>Kay
>
>  
>



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