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Re: port-arm/52666: ARM spinlocks are suboptimal
> On Oct 28, 2017, at 11:40 AM, coypu%SDF.ORG@localhost wrote:
>> Number: 52666
>> Category: port-arm
>> Synopsis: ARM spinlocks are suboptimal
>> Confidential: no
>> Severity: serious
>> Priority: medium
>> Responsible: port-arm-maintainer
>> State: open
>> Class: sw-bug
>> Submitter-Id: net
>> Arrival-Date: Sat Oct 28 18:40:00 +0000 2017
>> Originator: coypu
>> Release: NetBSD 8.99.5
> NetBSD 8.99.5
> newer ARM has an instruction 'wfe' essentially made for spinlocks. we should use it, but I don't see a relevant use of it, only an unused macro.
> (In fact only x86 has a spinlock backoff function).
Note that the sev 'send event' instruction needs to be used in parallel. When I experimented earlier I found that wfe/sev would many spurious wakeups negating advantages.
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