[PATCH] Xenoprof: Enabling performance profiling in Xen

[William Cohen <wcohen@redhat.com>]

I took a quick look at the patches for supporting profiling in Xen and I 
have some questions about the patches.

-Do all domains have to use the same setup for the performance 
monitoring counters? Or is there some virtualization of the performance 
counters?

-How is this going to interact with other performance monitoring 
infrastructure such as perfctr and perfmon? Or is the design going to 
need to be significantly revised for other performance monitoring 
interfaces? I like OProfile as much as anyone else, but I would like to 
see the Xen support allow the other interfaces to performance monitoring 
hardware to work.

-It appears that the multiple samples can be queued up in the 
hypervisor. In the OProfile kernel support when a process exits there is 
a flush of the per cpu buffers to make sure that the VMAs are mapped to 
files and offsets before the the mappings are lost. Should there be a 
flush of the samples from the hypervisor to make sure that they are read 
out before the process exits and the memory maps are lost?

-OProfile analysis tools expect the exectuable to be around when 
analyzing the sample files. Is the oprofile user space making the 
assumption that the domains have the same executables for the active and 
passive domains? Things could be messy if the domains are different, 
e.g. Fedora Core 3 domain and a Rawhide domain.

-Should get rid of xen-2.0.5/xen/arch/x86/oprofile/#Makefile# in the xen 
hypervisor patch.


-Will