[kvm-unit-tests,v2,0/2] s390x: Add exit time test

Message

Nico Boehr Sept. 1, 2022, 3:09 p.m. UTC

v1->v2:
---
* add missing cc clobber, fix constraints for get_clock_us() (thanks
  Thomas)
* avoid array and use pointer to const char* (thanks Thomas)
* add comment why testing nop makes sense (thanks Thomas)
* rework constraints and clobbers (thanks Thomas)

Sometimes, it is useful to measure the exit time of certain instructions
to e.g. identify performance regressions in instructions emulated by the
hypervisor.

This series adds a test which executes some instructions and measures
their execution time. Since their execution time depends a lot on the
environment at hand, all tests are reported as PASS currently.

The point of this series is not so much the instructions which have been
chosen here (but your ideas are welcome), but rather the general
question whether it makes sense to have a test like this in
kvm-unit-tests.

Nico Boehr (2):
  lib/s390x: time: add wrapper for stckf
  s390x: add exittime tests

 lib/s390x/asm/time.h |  11 +-
 s390x/Makefile       |   1 +
 s390x/exittime.c     | 255 +++++++++++++++++++++++++++++++++++++++++++
 s390x/unittests.cfg  |   4 +
 4 files changed, 270 insertions(+), 1 deletion(-)
 create mode 100644 s390x/exittime.c

Comments

Claudio Imbrenda Oct. 6, 2022, 11:18 a.m. UTC | #1

On Thu,  1 Sep 2022 17:09:54 +0200
Nico Boehr <[e-mail]> wrote:

> v1->v2:
> ---
> * add missing cc clobber, fix constraints for get_clock_us() (thanks
>   Thomas)
> * avoid array and use pointer to const char* (thanks Thomas)
> * add comment why testing nop makes sense (thanks Thomas)
> * rework constraints and clobbers (thanks Thomas)
> 
> Sometimes, it is useful to measure the exit time of certain instructions
> to e.g. identify performance regressions in instructions emulated by the
> hypervisor.
> 
> This series adds a test which executes some instructions and measures
> their execution time. Since their execution time depends a lot on the
> environment at hand, all tests are reported as PASS currently.
> 
> The point of this series is not so much the instructions which have been
> chosen here (but your ideas are welcome), but rather the general
> question whether it makes sense to have a test like this in
> kvm-unit-tests.

perhaps it makes sense to merge this patch series with your other one,
"s390x: Add migration test for guest TOD clock"

they both concern timing and reshuffling around and/or fixing timing
functions

> 
> Nico Boehr (2):
>   lib/s390x: time: add wrapper for stckf
>   s390x: add exittime tests
> 
>  lib/s390x/asm/time.h |  11 +-
>  s390x/Makefile       |   1 +
>  s390x/exittime.c     | 255 +++++++++++++++++++++++++++++++++++++++++++
>  s390x/unittests.cfg  |   4 +
>  4 files changed, 270 insertions(+), 1 deletion(-)
>  create mode 100644 s390x/exittime.c
>

Nico Boehr Oct. 11, 2022, 11:26 a.m. UTC | #2

Claudio,

Quoting Claudio Imbrenda (2022-10-06 13:18:56)
> perhaps it makes sense to merge this patch series with your other one,
> "s390x: Add migration test for guest TOD clock"
> 
> they both concern timing and reshuffling around and/or fixing timing
> functions

Since the TOD migration test is useful for regression testing my PV clock
fix[1], I would like to have this in ASAP. The exittime test, though, can wait
for a bit. If it's OK for you, I would like to keep these things seperate and
rather (re-)base the exittime test on the TOD migration test.

[1] https://lore.kernel.org/all/[e-mail]/