Messages in this thread | | | Date | Thu, 18 Dec 2014 23:03:08 -0500 | From | Dave Jones <> | Subject | Re: frequent lockups in 3.18rc4 |
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On Thu, Dec 18, 2014 at 10:58:59PM -0500, Dave Jones wrote: > > lock debugging and other overheads (does this still have > > DEBUG_PAGEALLOC?) you really are getting into a "real" softlockup > > because things are scaling so horribly badly. > > > > If you now disable spinlock debugging and lockdep, hopefully that page > > table lock now doesn't always get hung up on the lockdep locking, so > > it starts scaling much better, and maybe you'd not see this... > > I can give it a shot. Hopefully there's some further mitigation that > could be done to allow a workload like this to survive under a debug > build though, as we've caught *so many* bugs with this stuff in the past.
Turns out also that this build didn't have PROVE_LOCKING enabled. CONFIG_LOCKDEP was, but that just bloats the structures a little, and afaik doesn't incur the same runtime overhead.
I also forgot to answer the question above, PAGEALLOC is also off.
So the only thing that was on that could cause spinlock overhead was DEBUG_SPINLOCK (and LOCK_STAT, though iirc that's not huge either)
Dave
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