initial rusage patch.
Jeff Roberson
jroberson at chesapeake.net
Tue May 29 22:28:13 UTC 2007
http://people.freebsd.org/~jeff/rusage3.diff
I'm providing this patch for discussion only. I've just implemented
enough that you can see the fallout from this change. I have not yet
tested enough to say that this is perfect. I have also not yet fixed the
RLIMIT_CPU check in mi_switch().
You can see, however, that with this change there is no access to struct
proc in mi_switch() except for INVARIANTS and KTR. Aside, of course, for
the rlimit that needs to move anyway.
You can also see, that most access to rusage are done through fewer
indirects and to local memory. The storage impact of struct proc doesn't
change as pstat can be reclaimed as it could before.
Furthermore, the only time we need locks is in rufetch() where we
aggregate the threads counters and rusage structs into one allocated by
the caller. Doing this aggregation less frequently means we're touching
struct proc less frequently.
In this patch the scheduler lock protects this aggregation. In my
threadlock diff this will be protected by the per process spinlock and the
thread lock. However, in most places that we aggregate with calcru()
we're grabbing a spinlock anyway. So it is not so expensive to grab
another.
Thanks,
Jeff
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