Severe I/O overhead?

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

Both Jed and I have noticed a huge increase in latency for small I/O operations
in NetBSD/xen when compared to NetBSD/i386, even running in domain0.

One easy way to see this is to time the extraction followed by the removal
of pkgsrc with soft updates turned on.  The rm -rf takes about three times as
long in domain0 on both of our systems as it does running a "bare hardware"
kernel on the same machines.  The time isn't accounted as system time and I
have to guess that it's going to interrupt handling.

Does anyone see an obvious cause for this?  A cure?  I assume this is why
even though sequential I/O is not *that* much slower, and CPU-intensive
stuff obviously is just as fast, things like system and package builds are
so much slower under Xen than under NetBSD/i386.

-- 
 Thor Lancelot Simon                                          
tls%rek.tjls.com@localhost

"The inconsistency is startling, though admittedly, if consistency is to be
 abandoned or transcended, there is no problem."                - Noam Chomsky