On Fri, Jun 25, 2010 at 11:50:02AM +0200, Thomas Gleixner wrote: > On Fri, 25 Jun 2010, Nick Piggin wrote: > > On Thu, Jun 24, 2010 at 08:15:54PM +0200, Thomas Gleixner wrote: > > > On Thu, 24 Jun 2010, npiggin@xxxxxxx wrote: > > > > > > > +#define DEFINE_LGLOCK(name) \ > > > > + \ > > > > + DEFINE_PER_CPU(arch_spinlock_t, name##_lock); \ > > > > > > Uuurgh. You want to make that an arch_spinlock ? Just to avoid the > > > preempt_count overflow when you lock all cpu locks nested ? > > > > Yep, and the lockdep wreckage too :) > > > > Actually it's nice to avoid the function call too (lglock/brlocks > > are already out of line). Calls aren't totally free, especially > > on small chips without RSBs. And even with RSBs it's helpful not > > to overflow them, although Nehalem seems to have 12-16 entries. > > > > > > > I'm really not happy about that, it's going to be a complete nightmare > > > for RT. If you wanted to make this a present for RT giving the > > > scalability stuff massive testing, then you failed miserably :) > > > > Heh, it's a present for -rt because the locking is quite isolated > > (I did the same thing with hashtable bitlocks, added a new structure > > for them, in case you prefer spinlocks than bit spinlocks there). > > Sure, bitlocks are equally horrible. > > > -rt already changes locking primitives, so in the worst case you > > might have to tweak this. My previous patches were open coding > > these locks in fs/ so I can understand why that was a headache. > > I agree that having the code isolated makes my life easier, but I'm a > bit worried about the various new locking primitives which pop up in > all corners of the kernel. Be sure to shout at people for it :). Locking primitives really need to be reviewed, and having them in common places lets other people use them too. > > I think I'll keep it as is for now, it's hard enough to keep single > > threaded performance up. But it should be much easier to override > > this in -rt and I'll be happy to try restructuring things to help rt > > if and when it's possible. > > Ok, lets see how bad it gets :) Ok good. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
