On Wed, May 07, 2014 at 02:20:15PM -0700, j...@joshtriplett.org wrote:
> On Mon, Apr 28, 2014 at 05:24:54PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
> >
> > The current lock_torture_writer() spends too much time sleeping and not
> > enough time hammering locks, as in an eight-CPU test will often only be
> > utilizing a CPU or two. This commit therefore makes lock_torture_writer()
> > sleep less and hammer more.
> >
> > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> > ---
> > kernel/locking/locktorture.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> > index f26b1a18e34e..b0d3e3c50672 100644
> > --- a/kernel/locking/locktorture.c
> > +++ b/kernel/locking/locktorture.c
> > @@ -219,7 +219,8 @@ static int lock_torture_writer(void *arg)
> > set_user_nice(current, 19);
> >
> > do {
> > - schedule_timeout_uninterruptible(1);
> > + if ((torture_random(&rand) & 0xfffff) == 0)
> > + schedule_timeout_uninterruptible(1);
>
> That's a one-in-1048576 chance of sleeping for a jiffy; is that frequent
> enough to even bother sleeping at all?
On large systems, maybe not. Smallish systems should be able to get
through that loop a million times in a few hundreds of milliseconds,
though. So longer term a smarter approach might be needed, but this
should be a good start.
Thanx, Paul
> > cur_ops->writelock();
> > if (WARN_ON_ONCE(lock_is_write_held))
> > lwsp->n_write_lock_fail++;
> > --
> > 1.8.1.5
> >
>
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