[dpdk-dev] [21.08 PATCH v1 1/2] power: invert the monitor check

[Burakov, Anatoly]

On 25-May-21 10:15 AM, Liu, Yong wrote:
> 
> 
>> -----Original Message-----
>> From: dev <dev-bounces at dpdk.org> On Behalf Of Anatoly Burakov
>> Sent: Tuesday, May 11, 2021 11:32 PM
>> To: dev at dpdk.org; McDaniel, Timothy <timothy.mcdaniel at intel.com>; Xing,
>> Beilei <beilei.xing at intel.com>; Wu, Jingjing <jingjing.wu at intel.com>; Yang,
>> Qiming <qiming.yang at intel.com>; Zhang, Qi Z <qi.z.zhang at intel.com>;
>> Wang, Haiyue <haiyue.wang at intel.com>; Matan Azrad
>> <matan at nvidia.com>; Shahaf Shuler <shahafs at nvidia.com>; Viacheslav
>> Ovsiienko <viacheslavo at nvidia.com>; Richardson, Bruce
>> <bruce.richardson at intel.com>; Ananyev, Konstantin
>> <konstantin.ananyev at intel.com>
>> Cc: Loftus, Ciara <ciara.loftus at intel.com>
>> Subject: [dpdk-dev] [21.08 PATCH v1 1/2] power: invert the monitor check
>>
>> Previously, the semantics of power monitor were such that we were
>> checking current value against the expected value, and if they matched,
>> then the sleep was aborted. This is somewhat inflexible, because it only
>> allowed us to check for a specific value.
>>
>> We can reverse the check, and instead have monitor sleep to be aborted
>> if the expected value *doesn't* match what's in memory. This allows us
>> to both implement all currently implemented driver code, as well as
>> support more use cases which don't easily map to previous semantics
>> (such as waiting on writes to AF_XDP counter value).
>>
> 
> Hi Anatoly,
> In virtio spec, packed formatted descriptor utilizes two bits for representing the status. One bit for available status, one bit for used status.
> For checking the status more precisely, it is need to check value against the expected value.
> The monitor function in virtio datapath still can work with new semantics, but it may lead to some useless io call.
> Base on that, I'd like to keep previous semantics.
> 
> Regards,
> Marvin
> 

Thanks for your feedback! Would making this an option make things 
better? Because we need the inverted semantics for AF_XDP, it can't work 
without it. So, we either invert all of them, or we have an option to do 
regular or inverted check on a per-condition basis. Would that work?


-- 
Thanks,
Anatoly