[Xen-devel] Re: [PATCH 00/20] x86: ticket lock rewrite and paravirtualization

["H. Peter Anvin" <hpa@xxxxxxxxx>]

On 11/03/2010 07:59 AM, Jeremy Fitzhardinge wrote:
> 
>       - with an unmodified struct spinlock, it can check to see if
>         head == tail after unlock; if not, then there's someone else
>         trying to lock, and we can do a kick.  Unfortunately this
>         generates very high level of redundant kicks, because the
>         waiting CPU might not have blocked yet (which is the common
>         case)
> 

How high is "very high" here -- most of the time (so that any mitigation
on the slow patch is useless)?

        -hpa

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