Message ID | 20211222134520.587877-1-danielhb413@gmail.com (mailing list archive) |
---|---|
Headers | show |
Series | Re-write PPC64 PMU instruction count using TCG Ops | expand |
On 12/22/21 5:45 AM, Daniel Henrique Barboza wrote: > Hi, > > Two days ago Richard Henderson reported test failures with Avocado and > powernv8/9 due to timeouts [1]. The culprit ended up to be commit , a > commit where I introduced PMU instruction counting for TCG PPC64. > > For a reason that is still unclear to me these Avocado powernv tests are > suffering a huge performance impact after that patch, something that I > didn't verify in any other scenario I've tested. So one alternative to > fix the situation is to understand this difference and try to solve it, > which can take some time. > > Another alternative is to optimize the code introduced by that commit. > Today the instruction count is done by a TCG helper that is called after > each TB exit. I was aware that calling a helper frequently isn't > optimal, but that got the job done and didn't hindered the use of > pSeries and powernv machines. Well, until [1] at least. > > This series rewrites the PMU instruction counting using TCG Ops instead > of a TCG helper. To do that we needed to write in TCG Ops not only the > logic for increment the counters but also the logic to detect counter > overflows. > > A lot of code was added but the performance improvement is noticeable. > Using my local machine I did some test runs with the 2 Avocado powernv > tests that are timing out at this moment: You generate a *lot* of inline code here. Way too much, actually. If you can get this performance improvement with this reorg, it merely means that your original C algorithm was poor. The compiler should have been able to do better. I've tested this theory here and... > - failing Avocado powernv tests with current master: > > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (70.17 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (70.90 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (70.81 s) > > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (75.62 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (69.79 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (72.33 s) boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (75.73 s) boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (80.20 s) > - after this series: > > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (39.90 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (38.25 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (37.99 s) > > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (43.17 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (43.64 s) > (1/1) tests/avocado/boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (44.21 s) boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (39.66 s) boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (43.02 s) BTW, pre-power8-pmu, 29c4a3363b: boot_linux_console.py:BootLinuxConsole.test_ppc_powernv8: PASS (36.62 s) boot_linux_console.py:BootLinuxConsole.test_ppc_powernv9: PASS (39.69 s) I'll post my series shortly. r~