Re: "make check-acceptance" takes way too long

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> "make check-acceptance" takes way way too long. I just did a run
> on an arm-and-aarch64-targets-only debug build and it took over
> half an hour, and this despite it skipping or cancelling 26 out
> of 58 tests!
>
> I think that ~10 minutes runtime is reasonable. 30 is not;
> ideally no individual test would take more than a minute or so.
>
> Output saying where the time went. The first two tests take
> more than 10 minutes *each*. I think a good start would be to find
> a way of testing what they're testing that is less heavyweight.
>
>  (01/58) tests/acceptance/boot_linux.py:BootLinuxAarch64.test_virt_tcg_gicv2:
> PASS (629.74 s)
>  (02/58) tests/acceptance/boot_linux.py:BootLinuxAarch64.test_virt_tcg_gicv3:
> PASS (628.75 s)

So I've done some digging and tried some alternative images but I'm
running into two things:

 - -cpu max is slow without ,pauth-impdef=on
 - for some reason the distro cloud images cause 2 orders of magnitude more TB
   invalidates

For example a very simple Alpine boot:

  Translation buffer state:
  gen code size       810926227/1073659904
  TB count            1514678
  TB avg target size  17 max=2048 bytes
  TB avg host size    292 bytes (expansion ratio: 16.8)
  cross page TB count 0 (0%)
  direct jump count   1035828 (68%) (2 jumps=772419 50%)
  TB hash buckets     439751/524288 (83.88% head buckets used)
  TB hash occupancy   42.96% avg chain occ. Histogram: [0,10)%|▄▁█▁▁▇▁▅▁▂|[90,100]%
  TB hash avg chain   1.056 buckets. Histogram: 1|█▁  ▁▁|10

  Statistics:
  TB flush count      0
  TB invalidate count 550632
  TLB full flushes    0
  TLB partial flushes 1488833
  TLB elided flushes  12085180
  [TCG profiler not compiled]

which unsurprisingly has this at the top of the perf profile:

  20.17%  qemu-system-aar  qemu-system-aarch64      [.] do_tb_phys_invalidate   
   3.60%  qemu-system-aar  qemu-system-aarch64      [.] helper_lookup_tb_ptr
   
Versus my Debian Bullseye testing image (with all of systemd):

  Translation buffer state:
  gen code size       899208739/1073577984
  TB count            1599725
  TB avg target size  18 max=2048 bytes
  TB avg host size    318 bytes (expansion ratio: 17.2)
  cross page TB count 0 (0%)
  direct jump count   1067312 (66%) (2 jumps=826284 51%)
  TB hash buckets     816402/1048576 (77.86% head buckets used)
  TB hash occupancy   36.57% avg chain occ. Histogram: [0,10)%|▅ █  ▆▁▃▁▂|[90,100]%
  TB hash avg chain   1.027 buckets. Histogram: 1|█▁▁  ▁|9

  Statistics:
  TB flush count      0
  TB invalidate count 7763
  TLB full flushes    0
  TLB partial flushes 1066791
  TLB elided flushes  973569
  [TCG profiler not compiled]

with a more reasonable balance:

   4.21%  qemu-system-aar  qemu-system-aarch64         [.] get_phys_addr_lpae
   4.16%  qemu-system-aar  qemu-system-aarch64         [.] helper_lookup_tb_ptr

I'm open to ideas as to what might cause that.

-- 
Alex Bennée