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Date:   Fri, 22 Oct 2021 15:59:09 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Wanpeng Li <kernellwp@gmail.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Oleg Nesterov <oleg@redhat.com>,
        Ingo Molnar <mingo@kernel.org>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Wanpeng Li <wanpengli@tencent.com>
Subject: Re: [PATCH] rcuwait: do not enter RCU protection unless a wakeup is
 needed
Message-ID: <20211022135909.GB174703@worktop.programming.kicks-ass.net>
References: <20211020110638.797389-1-pbonzini@redhat.com>
 <YW/61zpycsD8/z4g@hirez.programming.kicks-ass.net>
 <98a72081-6a2b-b644-d029-edd03da84135@redhat.com>
 <CANRm+CyX+ZZh+LbLPBXEfMoExkx78qHpP-=yFCop9gX+LQeWDQ@mail.gmail.com>
 <bd4e3b80-fefd-43e8-e96b-ea81f21569bd@redhat.com>
 <CANRm+Cxpav5FqCBZoQv5BLnC160_RA3YDJc_CFabW7oMBFQ_5g@mail.gmail.com>
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On Wed, Oct 20, 2021 at 08:08:41PM +0800, Wanpeng Li wrote:
> On Wed, 20 Oct 2021 at 20:04, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > On 20/10/21 14:01, Wanpeng Li wrote:
> > > Yes, in the attachment.
> > >
> > >      Wanpeng
> >
> > This one does not have CONFIG_PREEMPT=y, let alone CONFIG_PREEMPT_RCU.
> > It's completely impossible that this patch has an effect without those
> > options.
> 
> Sorry, should be this one in the attachment.

Uhhmmm.. you have lockdep enabled. You know you shouldn't be doing
performance measurements with lockdep on, right?