[dpdk-dev] [PATCH v4 02/10] eal: add power management intrinsics

[Burakov, Anatoly]

On 08-Oct-20 6:15 PM, Ananyev, Konstantin wrote:
>>
>> Add two new power management intrinsics, and provide an implementation
>> in eal/x86 based on UMONITOR/UMWAIT instructions. The instructions
>> are implemented as raw byte opcodes because there is not yet widespread
>> compiler support for these instructions.
>>
>> The power management instructions provide an architecture-specific
>> function to either wait until a specified TSC timestamp is reached, or
>> optionally wait until either a TSC timestamp is reached or a memory
>> location is written to. The monitor function also provides an optional
>> comparison, to avoid sleeping when the expected write has already
>> happened, and no more writes are expected.
> 
> I think what this API is missing - a function to wakeup sleeping core.
> If user can/should use some system call to achieve that, then at least
> it has to be clearly documented, even better some wrapper provided.

I don't think it's possible to do that without severely overcomplicating 
the intrinsic and its usage, because AFAIK the only way to wake up a 
sleeping core would be to send some kind of interrupt to the core, or 
trigger a write to the cache-line in question.

-- 
Thanks,
Anatoly