Hi,
I'm trying power saving feature in my server with intel sapphire rapid CPU.
With "tsx=on" kernel parameter, I have both rtm and waitpkg available in CPU
flag.
I tried rte_power_monitor_multi API to monitor on multiple address, but it
never enters C0.2/C0.1 state.
To find the reason I patched the code to return the transaction abort code as
below:
/* transaction abort, possible write to one of wait addresses */
if (rc != RTE_XBEGIN_STARTED)
- return 0;
+ return rc;
and it turn out that RTM transaction always aborted with 0 (a few times with 4
or 6 also, which I think maybe expected due to memory change of monitored
addresses).
I found some explanation of the abort state here:
https://www.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/intrinsics/intrinsics-for-avx2/intrinsics-for-tsx/intrinsics-for-restrict-transactional-mem-ops/restricted-transactional-memory-overview.html
For abort code 0, it just say one example (CPUID used within transcation), but
it seems CPUID is not used within rte_power_monitor_multi.
I also tried rte_power_pause and rte_power_monitor, both works as expected, CPU
enters C0.2 state (checked by perf stat --e r20ec -C xx)
Now, I don't know why the RTM transaction aborted with 0 and don't know how to
debug it.
Can anyone throw some light on this?
Thank you.
Br, Xiaoping
