On Mon, Apr 29, 2019 at 10:19:44AM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-04-26 06:50:58 [-0700], Paul E. McKenney wrote:
> > One place to look is in the summary output:
> > 
> > TREE01 ------- 17540 GPs (58.4667/s) [rcu: g130629 f0x0 ]
> > 
> > The "58.4667/s" is the number of grace periods per second.  I would be
> > surprised if CONFIG_PARAVIRT_SPINLOCKS made a noticeable difference in
> > grace-period rate (given the natural variation), but you never know.
> 
> I did four runs of the different parts of the patch:
> - 5.1-rc6
> - #1 + kvm64 CPU + some config options
> - #2 + tsc-deadline=on and so on (the whole line)
> - #3 + CONFIG_PARAVIRT_SPINLOCKS (now everything)
> 
> the test command was
> 	tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 112 --duration 60 --configs "16*TREE08" --memory 4G
> 
> and the results:
> | HEAD is now at 085b7755808a... Linux 5.1-rc6
> | (28.5942 +27.4658 +28.0203 +27.2061 +28.0731 +26.9078 +27.8494 + 27.3392 +26.4339 +28.025 +27.4797 +27.6775 +28.0653 +28.0742 +27.9581 +28.6508)/ 16
> | 27.738775
> | 
> | HEAD is now at 36a12aa9761a... tune #1
> | (28.5761 +26.6514 +26.6989 +27.4375 +27.3442 +28.3228 +26.6353 +27.5461+28.5531 +27.7006 +27.8078 +27.9753 +27.4269 +28.0464 +27.6314 +27.8356) / 16
> | 27.6368375
> | 
> | HEAD is now at af5cd7196436... tune #2
> | (28.4867 +26.3675 +27.6364 +28.3344 +27.4153 +27.9306 +27.1703 +26.8461+27.3194 +28.5486 +27.8975 +27.4356 +28.12 +28.4397 +29.0186 +26.9328 )/ 16
> | 27.74371875
> | 
> | HEAD is now at 3701f64943f5... tune #3
> | (28.2431 +27.7831 +28.39 +28.2586 +27.7408 +27.9258 +26.6236 +26.7817+29.1178 +26.9564 +29.0525 +27.4258 +27.4931 +27.8928 +26.9308 +28.4833)/ 16
> | 27.8187
> 
> This 28.… is the number of GP/s. Based on the results in looks like
> noise to me. Also I have no idea why you have more than twice as many
> GP/s as I do.

My guess is that because you have more CPUs, the for_each_online_cpu()
loop takes longer on your system.

> Different box doing:
> 	tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 112 --duration 60 --configs "42*TREE01" --memory 4G
> and got this:
> 
> | HEAD is now at 085b7755808aa... Linux 5.1-rc6
> | (15.2878 + 15.8664 + 15.6369 + 15.6714 + 15.3667 + 16.4706 + 15.7844 +
> | 16.2119 + 15.6108 + 15.84 + 16.0003 + 16.2886 + 15.8728 + 15.5347 +
> | 15.6753 + 15.6628 + 15.8628 + 15.8158 + 15.8419 + 16.0053 + 15.7878 +
> | 16.465 + 16.2267 + 16.6881 + 16.3186 + 16.1778 + 15.7069 + 16.0178 +
> | 15.7156 + 16.0083 + 15.7181 + 15.8961 + 15.5253 + 16.1569 + 15.7692 +
> | 16.2622 + 16.2931 + 15.9531 + 15.6697 + 15.4539 + 15.6478 + 15.8047) /
> | 42
> |	~15.89452142857142857143
> |
> | HEAD is now at 3701f64943f5a... tune #3
> | ; (15.8461 + 15.8653 + 16.0392 + 15.8906 + 15.7606 + 15.6169 + 16.1425 +
> | 15.9089 + 16.2169 + 16.1694 + 16.2122 + 15.6417 + 15.8022 + 16.1178 +
> | 15.1689 + 16.1303 + 16.0181 + 16.3797 + 16.0614 + 16.2839 + 15.4583 +
> | 15.9178 + 16.0589 + 16.3428 + 15.5486 + 16.0839 + 15.9931 + 15.8417 +
> | 16.0981 + 15.8075 + 15.9925 + 15.7311 + 15.9172 + 16.1164 + 15.6303 +
> | 15.9383 + 16.0714 + 16.2786 + 15.8394 + 15.9597 + 16.0175 + 15.3908) /
> | 42
> |	~15.93586904761904761905
> 
> Noise.
> 
> So from RCUtorture point of view there is no improvement right? In that
> case I would suggest to drop the problematic parts…

Thank you for testing this!  I will adjust accordingly.

							Thanx, Paul