Date: Mon, 29 Sep 2008 13:22:33 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: freebsd-hackers@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG, danny@cs.huji.ac.il, Jeremy Chadwick <koitsu@FreeBSD.ORG>, kris@FreeBSD.org Subject: Re: bad NFS/UDP performance Message-ID: <alpine.BSF.1.10.0809291321030.48735@fledge.watson.org> In-Reply-To: <200809291158.m8TBwped076763@lurza.secnetix.de> References: <200809291158.m8TBwped076763@lurza.secnetix.de>
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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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