[PATCH v2] mempool: fix get objects from mempool with cache

[Morten Brørup]

> From: Andrew Rybchenko [mailto:andrew.rybchenko at oktetlabs.ru]
> Sent: Tuesday, 4 October 2022 17.59
> 
> On 10/4/22 18:13, Morten Brørup wrote:
> > @Aaron, do you have any insights or comments to my curiosity below?
> >
> >> From: Andrew Rybchenko [mailto:andrew.rybchenko at oktetlabs.ru]
> >> Sent: Tuesday, 4 October 2022 14.58
> >>
> >> Hi Morten,
> >>
> >> In general I agree that the fix is required.
> >> In sent v3 I'm trying to make it a bit better from my point of
> >> view. See few notes below.
> >
> > I stand by my review and accept of v3 - this message is not intended
> to change that! I'm just curious...
> >
> > I wonder how accurate the automated performance tests ([v2], [v3])
> are, and if they are comparable between February and October?
> >
> > [v2]: http://mails.dpdk.org/archives/test-report/2022-
> February/256462.html
> > [v3]: http://mails.dpdk.org/archives/test-report/2022-
> October/311526.html
> >
> >
> > Ubuntu 20.04
> > Kernel: 4.15.0-generic
> > Compiler: gcc 7.4
> > NIC: Intel Corporation Ethernet Converged Network Adapter XL710-QDA2
> 40000 Mbps
> > Target: x86_64-native-linuxapp-gcc
> > Fail/Total: 0/4
> >
> > Detail performance results:
> > ** V2 **:
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | num_cpus | num_threads | txd/rxd | frame_size |  throughput
> difference from  |
> > |          |             |         |            |           expected
> |
> >
> +==========+=============+=========+============+======================
> ========+
> > | 1        | 2           | 512     | 64         | 0.5%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 2           | 2048    | 64         | -1.5%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 1           | 512     | 64         | 4.3%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 1           | 2048    | 64         | 10.9%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> >
> > ** V3 **:
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | num_cpus | num_threads | txd/rxd | frame_size |  throughput
> difference from  |
> > |          |             |         |            |           expected
> |
> >
> +==========+=============+=========+============+======================
> ========+
> > | 1        | 2           | 512     | 64         | -0.7%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 2           | 2048    | 64         | -2.3%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 1           | 512     | 64         | 0.5%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> > | 1        | 1           | 2048    | 64         | 7.9%
> |
> > +----------+-------------+---------+------------+--------------------
> ----------+
> >
> 
> Very interesting, may be it make sense to sent your patch and
> mine once again to check current figures and results stability.
> 

V2 retest:

http://mails.dpdk.org/archives/test-report/2022-October/311609.html

Ubuntu 20.04
Kernel: 4.15.0-generic
Compiler: gcc 7.4
NIC: Intel Corporation Ethernet Converged Network Adapter XL710-QDA2 40000 Mbps
Target: x86_64-native-linuxapp-gcc
Fail/Total: 0/4

Detail performance results: 
+----------+-------------+---------+------------+------------------------------+
| num_cpus | num_threads | txd/rxd | frame_size |  throughput difference from  |
|          |             |         |            |           expected           |
+==========+=============+=========+============+==============================+
| 1        | 2           | 512     | 64         | 0.1%                         |
+----------+-------------+---------+------------+------------------------------+
| 1        | 2           | 2048    | 64         | -3.0%                        |
+----------+-------------+---------+------------+------------------------------+
| 1        | 1           | 512     | 64         | -3.7%                        |
+----------+-------------+---------+------------+------------------------------+
| 1        | 1           | 2048    | 64         | 8.1%                         |
+----------+-------------+---------+------------+------------------------------+

Probably not very accurate.

And 8.1% is very close to the V3 7.9% - nothing to worry about, compared to the previous v2 test result of 10.9%.

-Morten