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Date: Fri, 6 Nov 2015 16:36:24 +0530
Message-ID: <CAGZKiBrHLKvOfxrB9juKzS3v_gdp-jfKFGH8TGNB-4zOiDUWbA@mail.gmail.com>
From: Bharata B Rao <bharata.rao@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH v9 00/56] Postcopy implementation
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, quintela@redhat.com, liang.z.li@intel.com, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, luis@cs.umu.se, Bharata B Rao <bharata@linux.vnet.ibm.com>, "amit.shah@redhat.com" <amit.shah@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, David Gibson <david@gibson.dropbear.id.au>

On Fri, Nov 6, 2015 at 2:39 PM, Dr. David Alan Gilbert
<dgilbert@redhat.com> wrote:
> * Bharata B Rao (bharata@linux.vnet.ibm.com) wrote:
>> On Thu, Nov 05, 2015 at 06:10:27PM +0000, Dr. David Alan Gilbert (git) wrote:
>> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>> >
>> >   This is the 9th cut of my version of postcopy.
>> >
>> > The userfaultfd linux kernel code is now in the upstream kernel
>> > tree, and so 4.3 can be used without modification.
>> >
>> > This qemu series can be found at:
>> > https://github.com/orbitfp7/qemu.git
>> > on the wp3-postcopy-v9 tag
>> >
>> > Testing status:
>> >   * Tested heavily on x86
>> >   * Smoke tested on aarch64 (so it does work on different page sizes)
>>
>> Tested minimally on ppc64 with back and forth postcopy migration of
>> unloaded pseries guest within the localhost - works as expected.
>>
>> However I am seeing a failure in one case. I am not sure if this is
>> a user error or a real issue in postcopy migration. If I switch to postcopy
>> migration immediately after starting the migration, I see the migration
>> failing with error:
>>
>> qemu-system-ppc64: qemu_savevm_send_packaged: Unreasonably large packaged state: 25905005
>
> I put an arbitrary limit of 16MB (see MAX_VM_CMD_PACKAGED_SIZE in include/sysemu/sysemu.h)
> on the size of the data accepted into the packaged blob.  How big is the htab data likely to be?

HTAB size is a variable and depends on maxmem size. It will be 1/128
th of maxmem. So for a 32G guest, HTAB will be 256M in size.

Regards,
Bharata.