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. > 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 :) Thanks, tglx -- 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
