From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paul Mackerras <paulus@ozlabs.org>
Date: Tue, 18 Dec 2018 01:02:11 +0000
Subject: Re: [PATCH 0/4] KVM: PPC: Book3S HV: Improve live migration of radix guests
Message-Id: <20181218010211.GD25748@blackberry>
List-Id: <kvm-ppc.vger.kernel.org>
References: <20181212041430.GA22265@blackberry>
In-Reply-To: <20181212041430.GA22265@blackberry>
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To: kvm-ppc@vger.kernel.org

On Wed, Dec 12, 2018 at 03:14:30PM +1100, Paul Mackerras wrote:
> We have observed that live migration of radix guests tends to converge
> slowly and sometimes doesn't converge at all.  This appears to be due
> largely to the fact that if the host is using transparent huge pages,
> page dirtiness only gets tracked with a 2MB granularity for the parts
> of the guest memory that are mapped using 2MB pages.  The fix is to
> break down the mappings in the partition-scoped page tables to 64k
> pages (or 4k pages if 4k is the system page size).  This is
> accomplished by flushing the partition-scoped page tables when turning
> dirty page tracking on or off, and by only inserting small-page PTEs
> into the partition-scoped page tables while dirty page tracking is
> enabled.
> 
> Paul.

Series applied to my kvm-ppc-next branch.

Paul.