One of the concerns about the measurement being produced by perfmon2 is that they are correct (or close enough for government work:). Given the variety of events that the performance monitoring hardware measures just getting events that provide verifiable counts for user-space only can be a challenge. The testing framework has events for various processors that can be counted in some repeatable manner.
I looking at testing the privilege level mask filtering for user- and kernel-space. The test code doesn't know what code is running in the kernel. Thus, trying to do repeatable counts is not going to be possible. Thinking through what possible failure modes there could be for the user/kernel space event filtering: -Count perfmon event when not suppose to -Not count perfmon event when suppose to The number of events is not known and could vary because of the kernel code. One thought is to compare multiple measurement on a run to see that the values are consistent and sane: * user-space only count <= user+kernel+space count * kernel-space only count <= user+kernel+space count * no-space count == 0 These experiments should be run twice: one set with an event that is only triggered in the user-space (e.g. FP op counting) and a second set an event that occurs both in kernel and user space. Any thoughts or comments about testing this area of perfmon? -Will _______________________________________________ perfmon mailing list [email protected] http://www.hpl.hp.com/hosted/linux/mail-archives/perfmon/
