The current set of Perfmon2 patches have changes that touch core parts of the
kernel due to the per thread support (scheduler and task struct). I am wondering
if splitting perfmon set that has the basic perfmon interface but only allows
system-wide setting of the performance monitoring hardware and per thread
support patches would be a worthwhile. Would this be a logical way to further
break down the perfmon2 patches?
Having the system-wide only subset could still be useful in sampling systems
such as OProfile. It would also avoid changing the task struct which changes
kernel abi/data structures. In theory something like this could be seperate
module that the rest of the kernel could be fairly ignorant of (with the
exception of resource allocation for nmi timer).
Have a second set of patches that add the per-thread support on top of the
systemwide only patches. There are definitely applications were this type of
support is very desirable, e.g. allowing normal people to use the performance
monitoring hardware to see what is going on within a single thread. System-wide
requires root access and can muddle the results from different threads.
-Will
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