On Thu, Oct 31, 2013 at 12:14:15PM +0100, Paolo Bonzini wrote: > Il 30/10/2013 20:09, Michael S. Tsirkin ha scritto: > > I noticed that srcu_read_lock/unlock both have a memory barrier, > > so just by moving srcu_read_unlock earlier we can get rid of > > one call to smp_mb(). > > > > Unsurprisingly, the gain is small but measureable using the unit test > > microbenchmark: > > before > > vmcall 1407 > > after > > vmcall 1357 > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > Across how many runs? It's the experiment that vmexit test does: it runs for 2^30 cycles, then divides the number of cycles by the number of iterations. You get in the ballpark of 1300000 iterations normally. > Best or average or "all runs were in that > ballpark", :) and what's the minimum/maximum before and after the patch? > > As you say the benefit is not surprising, but the experiments should be > documented properly. > > Paolo "All runs in that ballpark". -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
