Re: [PATCH v3] cpupower: fix TSC MHz calculation

From: Shuah
Date: Mon Dec 16 2024 - 16:09:09 EST


On 12/11/24 19:14, He Rongguang wrote:
Commit 'cpupower: Make TSC read per CPU for Mperf monitor' (c2adb1877b7)
changes TSC counter reads per cpu, but left time diff global (from start
of all cpus to end of all cpus), thus diff(time) is too large for a
cpu's tsc counting, resulting in far less than acutal TSC_Mhz and thus
`cpupower monitor` showing far less than actual cpu realtime frequency.

/proc/cpuinfo shows frequency:
cat /proc/cpuinfo | egrep -e 'processor' -e 'MHz'
...
processor : 171
cpu MHz : 4108.498
...

before fix (System 100% busy):
| Mperf || Idle_Stats
CPU| C0 | Cx | Freq || POLL | C1 | C2
171| 0.77| 99.23| 2279|| 0.00| 0.00| 0.00

after fix (System 100% busy):
| Mperf || Idle_Stats
CPU| C0 | Cx | Freq || POLL | C1 | C2
171| 0.46| 99.54| 4095|| 0.00| 0.00| 0.00

Fixes: c2adb1877b76 ("cpupower: Make TSC read per CPU for Mperf monitor")
Signed-off-by: He Rongguang <herongguang@xxxxxxxxxxxxxxxxx>
---

Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux.git/log/?h=cpupower
to be included in my next pull request to Rafael.

thanks,
-- Shuah