The Samba-Bugzilla – Bug 5587
Excessive hotplug events
Last modified: 2008-07-15 11:43:34 UTC
Using samba 3.0.30 on a fileserver with any 2.6.25+ kernel, as soon as a user connects from windows (2000,XP) and tries to get the properties of a lot of files at once, the performance is horrible, and the server is throwing hundreds of thousands of hotplug events per second.
Samba 3.0.10 was not affected, 3.0.26 and 3.0.30 are, have not tested other versions.
Disabling hotplug altogether ('echo > /proc/sys/kernel/hotplug') restores performance to normal levels, but that does not seem the right thing to do.
Figured out how to get around it - disabling the 'Group CPU Scheduler' (GROUP_SCHED) and recompiling the entire kernel stops the hotplug events, and performance is back to normal on this box.