Re: [Qemu-devel] [PATCH v9 00/56] Postcopy implementation

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

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

1. (qemu) migrate_set_capability x-postcopy-ram on

2. (qemu) migrate -d tcp:localhost:4444

3. (qemu) info migrate
capabilities: xbzrle: off rdma-pin-all: off auto-converge: off zero-blocks: off compress: off events: off x-postcopy-ram: on 
Migration status: active
total time: 4177 milliseconds
expected downtime: 300 milliseconds
setup: 75 milliseconds
transferred ram: 115523 kbytes
throughput: 155.69 mbps
remaining ram: 30117196 kbytes
total ram: 33554688 kbytes
duplicate: 835311 pages
skipped: 0 pages
normal: 24061 pages
normal bytes: 96244 kbytes
dirty sync count: 1

4. (qemu) migrate_start_postcopy

5. (qemu) info migrate
capabilities: xbzrle: off rdma-pin-all: off auto-converge: off zero-blocks: off compress: off events: off x-postcopy-ram: on 
Migration status: failed
total time: 0 milliseconds

If I run 'info migrate' in step 3 a few more times before step 4, then
the migration succeeds. So is there a way to figure out when to switch
over to postcopy migration ?

QEMU cmdline: ./ppc64-softmmu/qemu-system-ppc64 --enable-kvm --nographic -vga none -machine pseries -m 32G,slots=32,maxmem=64G -smp 16 -device virtio-blk-pci,drive=rootdisk -drive file=/home/bharata/F20-snap1,if=none,cache=none,id=rootdisk,format=qcow2 -monitor telnet:127.0.0.1:1234,server,nowait

Host: 4.3.0-rc7+ 

Regards,
Bharata.