On Sun, 12 Apr 2009, Poul-Henning Kamp wrote:
In message <[email protected]>, Robert
Wats on writes:
I have a project along these lines in progress, and will post the proposal
to arch@ once I've finished prototyping it. In particular, it provides
common implementations of "reset" and "report" in order to expose a single
userspace version of the structure via sysctl.
Please don't export them via sysctl.
Export them via mmap(2) like we already do with the disk I/O statistics.
That way monitoring the counters becomes a no-syscall operation.
The sysctls already exist, and are used by both built-in and third-party
monitoring tools. Given the 8.0 timeline and the list of other things to get
done before 8.0, I'm happy to solve the per-CPU counter problem as it is
necessary to do so, but I don't have time to solve the mmap'd per-CPU counter
problem, as it's not necessary to do so. In the current design the per-CPU
counter framework allocates the storage for the counters, so it should be easy
to add that feature later.
Robert N M Watson
Computer Laboratory
University of Cambridge
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