On Tue, 6 Jan 2026 14:48:14 -0500 Peter Xu <[email protected]> wrote:
> On Sun, Jan 04, 2026 at 01:44:52PM +0800, Zhang Chen wrote: > > On Tue, Dec 30, 2025 at 11:02 PM Peter Xu <[email protected]> wrote: > > > > > > On Tue, Dec 30, 2025 at 03:05:43PM +0100, Lukas Straub wrote: > > > > Hello everyone, > > > > This adds COLO multifd support and migration unit tests for COLO > > > > migration > > > > and failover. > > > > > > Hi, Lukas, > > > > > > I'll review the series after the new year. > > > > > > Could you still introduce some background on how you're deploying COLO? > > > Do > > > you use it in production, or for fun? > > > > > > COLO is still a nice and interesting feature, said that, COLO has quite a > > > lot of code plugged into migration core. I wished it's like a multifd > > > compressor which was much more self-contained, but it's not. I wished we > > > can simplify the code in QEMU migration. > > > > > > We've talked it through before with current COLO maintainers, it looks to > > > me there aren't really much users using it in production, meanwhile COLO > > > doesn't look like a feature to benefit individual QEMU users either. > > > > > > I want to study the use case of COLO in status quo, and evaluate how much > > > effort we should put on it in the future. Note that if it's for fun we > > > can > > > always use a stable branch which will be there forever. We'll need to > > > think about QEMU evolving in the future, and what's best for QEMU. > > > > > > Thanks, > > > > > > > Hi Lukas and Peter, > > Hi, Chen, > > > > > Thanks for this series, I will support for background info if Peter > > have any questions. > > Thanks, I believe my major question so far was, whether we should deprecate > COLO in migration framework. :) > > The netfilters and rest can be discussed separately. > > Now looking back at my initial ask in Zhijian's fix, I still agree with > Zhijian on these two points mentioned: > > https://lore.kernel.org/all/[email protected]/ > > That is: > > - Active users who depend on it. > - A unit test for the COLO framework. > > Meanwhile, I can't see how COLO would win if to be compared with some > app-level HA infrastructure.. considering the overhead it requires on > running two VMs and compare every packet. > > Lukas, thanks for trying to fix the 2nd. I apologize that I still > requested you to send these patches, without further raising the attention > that I still want to discuss deprecation. I don't think anyone yet proved > we should keep COLO. I do plan to send one patch adding COLO framework to > deprecation, if nobody would stop me in a week justifying question 1 above. Hello Peter, I am a consultant on open-source high availability and fault tolaerance solutions. I provide a complete cluster management solution with automatic failover and failback for Qemu COLO. Qemu COLOs lockstepping architecture has a big performance advantage and it outperforms the market leader by 10x-100x in latency. No one else provides this unique architecture. I have customers that depend on this. I occasionally get inquiries about Qemu COLO even without doing any kind of marketing. So there is a general interest for this. Also, Canonical considers providing this to one of their customers. Regards, Lukas Straub > > We kind of proved almost nobody is actively using COLO anymore in the past > few releases. If nobody is using COLO, we should simply drop it. > > > And CC Hailiang Zhang, although he hasn't replied to emails for a long time. > > If no one objects, I think Lukas can replease Hailiang for COLO Framework. > > > > COLO Framework > > M: Hailiang Zhang <[email protected]> > > S: Maintained > > F: migration/colo* > > F: include/migration/colo.h > > F: include/migration/failover.h > > F: docs/COLO-FT.txt > > Right, this is also another reason why I think we may want to deprecate > COLO framework. I will take over maintainership. > > Since I requested this series (sorry again, Lukas), I'll review it today no > matter if we decide to merge this series at last, or deprecate COLO > framework. > > Thanks, > > > > > Thanks > > Chen > > > > > > > > > > Regards, > > > > Lukas > > > > > > > > Signed-off-by: Lukas Straub <[email protected]> > > > > --- > > > > Lukas Straub (3): > > > > multifd: Add colo support > > > > migration-test: Add -snapshot option for COLO > > > > migration-test: Add COLO migration unit test > > > > > > > > migration/meson.build | 2 +- > > > > migration/multifd-colo.c | 57 ++++++++++++++++++ > > > > migration/multifd-colo.h | 26 +++++++++ > > > > migration/multifd.c | 14 ++++- > > > > tests/qtest/meson.build | 7 ++- > > > > tests/qtest/migration-test.c | 1 + > > > > tests/qtest/migration/colo-tests.c | 115 > > > > +++++++++++++++++++++++++++++++++++++ > > > > tests/qtest/migration/framework.c | 69 +++++++++++++++++++++- > > > > tests/qtest/migration/framework.h | 10 ++++ > > > > 9 files changed, 294 insertions(+), 7 deletions(-) > > > > --- > > > > base-commit: 942b0d378a1de9649085ad6db5306d5b8cef3591 > > > > change-id: 20251230-colo_unit_test_multifd-8bf58dcebd46 > > > > > > > > Best regards, > > > > -- > > > > Lukas Straub <[email protected]> > > > > > > > > > > -- > > > Peter Xu > > > > > >
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