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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/