On Thursday 30 November 2006 02:25, Paul E. McKenney wrote:
> On Wed, Nov 22, 2006 at 04:02:29PM +0100, Eric Dumazet wrote:
> > On some workloads, (for example when lot of close() syscalls are done),
> > RCU qlen can be quite large, and RCU heads are no longer in cpu cache
> > when rcu_do_batch() is called.
> >
> > This patches adds a prefetch() in rcu_do_batch() to give CPU a hint to
> > bring back cache lines containing 'struct rcu_head's.
> >
> > Most list manipulations macros include prefetch(), but not open coded
> > ones (at least with current C compilers :) )
> >
> > I got a nice speedup on a trivial benchmark (3.48 us per iteration
> > instead of 3.95 us on a 1.6 GHz Pentium-M)
> > while (1) { pipe(p); close(fd[0]); close(fd[1]);}
>
> Interesting! How much of the speedup was due to the prefetch() and how
> much to removing the extra store to rdp->donelist?
I only benchmarked the prefetch() case.
Then, when cooking the patch I found I could do the rdp->donelist affectation
after the loop. I am not sure it's worth to do another benchmark for this
trivial optimization (Please dont tell me its not a valid one :) )
Eric
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
