From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NFTaH-00037N-7a for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:20:05 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NFTaB-000331-Aq for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:20:04 -0500 Received: from [199.232.76.173] (port=56912 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NFTaA-00032u-TX for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:19:58 -0500 Received: from david.siemens.de ([192.35.17.14]:24326) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NFTaA-0005cR-HG for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:19:58 -0500 Message-ID: <4B15260B.9050104@siemens.com> Date: Tue, 01 Dec 2009 15:19:55 +0100 From: Jan Kiszka MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH] live migration: Serialize vmstate saving in stage 2 List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel , Liran Schour , Pierre Riteau The effect of this patch with current block migration is that its stage 2, ie. the first full walk-through of the block devices will be performed completely before RAM migration starts. This ensures that continuously changing RAM pages are not re-synchronized all the time while block migration is not completed. Future versions of block migration which will respect the specified downtime will generate a different pattern: After RAM migration has started as well, block migration may also continue to inject dirty blocks into the RAM stream once it detects that the number of pending blocks would extend the downtime unacceptably. Note that all this relies on the current registration order: block before RAM migration. Signed-off-by: Jan Kiszka --- savevm.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/savevm.c b/savevm.c index 3fee38c..930543e 100644 --- a/savevm.c +++ b/savevm.c @@ -1293,7 +1293,14 @@ int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f) qemu_put_byte(f, QEMU_VM_SECTION_PART); qemu_put_be32(f, se->section_id); - ret &= !!se->save_live_state(mon, f, QEMU_VM_SECTION_PART, se->opaque); + ret = se->save_live_state(mon, f, QEMU_VM_SECTION_PART, se->opaque); + if (!ret) { + /* Do not proceed to the next vmstate before this one reported + completion of the current stage. This serializes the migration + and reduces the probability that a faster changing state is + synchronized over and over again. */ + break; + } } if (ret)