On Tue, Mar 22, 2016 at 06:31:54AM +0100, Borislav Petkov wrote: > On Mon, Mar 21, 2016 at 09:42:09PM +0000, Chris Bainbridge wrote: > > Hi, > > > > I was testing something on an old server (Dell T105 opteron) and noticed > > packet loss after updating the kernel from 3.10 to 4.5. The test was: > > > > On Dell run: iperf -s > > On another system: iperf3 -c dell -u -b 20M -l 1k -t 1000 > > > > This sends a 20mbit UDP stream to the Dell. It works fine normally (0% > > packet loss), but when CONFIG_PROVE_LOCKING is enabled there is high > > (35%) packet loss. (DEBUG_LOCKDEP also seems to cause packet loss) > > > > The packet loss bisected back to: > > > > commit 88d84ac97378c2f1d5fec9af1e8b7d9a662d6b00 > > Author: Borislav Petkov <[email protected]> > > Date: Fri Jul 19 12:28:25 2013 +0200 > > > > EDAC: Fix lockdep splat > > Hmm, how would that cause a packet loss?!
The previous bug would disable lockdep and thereby avoid much of the normal overhead associated with lockdep. I suspect the packet loss is a result of increased overhead. IOW, everything works as expected.
