Re: [rfc 19/45] cpu alloc: NFS statistics

Trond Myklebust
2007-11-20T21:47:46Z

On Tue, 2007-11-20 at 16:28 -0500, Mathieu Desnoyers wrote:
> * Trond Myklebust (trond.myklebust@fys.uio.no) wrote:
> >
> > On Tue, 2007-11-20 at 12:49 -0800, Christoph Lameter wrote:
> > > On Tue, 20 Nov 2007, Mathieu Desnoyers wrote:
> > >
> > > > > Index: linux-2.6/fs/nfs/iostat.h
> > > > > ===================================================================
> > > > > --- linux-2.6.orig/fs/nfs/iostat.h 2007-11-15 21:17:24.391404458 -0800
> > > > > +++ linux-2.6/fs/nfs/iostat.h 2007-11-15 21:25:33.167654066 -0800
> > > > > @@ -123,7 +123,7 @@ static inline void nfs_inc_server_stats(
> > > > > int cpu;
> > > > >
> > > > > cpu = get_cpu();
> > > > > - iostats = per_cpu_ptr(server->io_stats, cpu);
> > > > > + iostats = CPU_PTR(server->io_stats, cpu);
> > > > > iostats->events[stat] ++;
> > > >
> > > > Is there a way to change this into a CPU_ADD ?
> > >
> > > Yes I must have missed that.
> > >
> > > Could be
> > >
> > > CPU_INC(server->io_stats->events[stat]);
> > >
> > > >
> > > > > put_cpu_no_resched();
> > > >
> > > > Why put_cpu_no_resched here ?
> > >
> > > We do not want to reschedule here? We may have already disabled interrupts
> > > or some such thing.
> >
> > Some of these statistics are updated from inside a spinlocked
> > environment, hence the put_no_resched().
> >
>
> The we could use __get_cpu_var instead ? (since we know preemption is
> _always_ disabled when we are called) ?

We don't know that. I said that _some_ of these statistics are updated
in that way.

Cheers
Trond