Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] KVM: x86: use TPAUSE to replace PAUSE in halt polling | Date | Wed, 24 Aug 2022 14:08:16 +0000 |
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From: Dapeng Mi > Sent: 24 August 2022 10:11 > > TPAUSE is a new instruction on Intel processors which can instruct > processor enters a power/performance optimized state. Halt polling > uses PAUSE instruction to wait vCPU is waked up. The polling time > could be long and cause extra power consumption in some cases. > > Use TPAUSE to replace the PAUSE instruction in halt polling to get > a better power saving and performance.
What is the effect on wakeup latency? Quite often that is far more important than a bit of power saving.
The automatic entry of sleep states is a PITA already. Block 30 RT threads in cv_wait() and then do cv_broadcast(). Use ftrace to see just how long it takes the last thread to wake up.
David
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