On Mon, 29 Sep 2008, Oliver Fromme wrote:
Danny Braniss wrote:
> Grr, there goes binary search theory out of the window,
> So far I have managed to pinpoint the day that the changes affect the
> throughput:
> 18/08/08 00:00:00 19/08/08 00:00:00
> (I assume cvs's date is GMT).
> now would be a good time for some help, specially how to undo changes, my
> knowledge of csup/cvs are close to zero.
So you've nailed to down to this 24-hour window:
http://www.secnetix.de/olli/FreeBSD/svnews/?day=2008-08-18&p=/stable/7
I'm afraid that r181822 by rwatson is the most likely candidate that might
be causing the regression.
If we can confirm that it was that specific change, then I can create a patch
to restore exclusive locking for UDP and we can see if it was the general move
to rwlocking, or specifically the read-locking of certain data structures.
Perhaps what we've done is moved contention from a mutex to a sleep lock,
reducing the efficiency of handling contention? Adding Kris to the CC line
because he often has useful insights on this sort of thing.
Robert N M Watson
Computer Laboratory
University of Cambridge
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