Message-ID: <1335885103.13683.147.camel@twins>
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
Cc: "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>, mingo@elte.hu,
        jeremy@goop.org, mtosatti@redhat.com, kvm@vger.kernel.org,
        x86@kernel.org, vatsa@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
        hpa@zytor.com
Date: Tue, 01 May 2012 17:11:43 +0200
In-Reply-To: <4F9FD337.5010908@redhat.com>
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On Tue, 2012-05-01 at 15:12 +0300, Avi Kivity wrote:
> We're now moving the freeing of kvm shadow page tables from using rcu to
> using an irq-protected scheme like gup_fast(), because of the
> performance differences.  We didn't track it down but I expect the cause
> is less reuse of cache-hot pages. 

It would be good to understand these things.. just doing things because
tends to come back and bite you :-)

If its cache behaviour you should be able to clearly see that using perf
stat.
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