Re: [Qemu-devel] [RFC] migration next tree

[Orit Wasserman]

On 06/22/2012 11:43 PM, Vinod Chegu wrote:
> 
> 
> On Fri, Jun 22, 2012 at 6:59 AM, Juan Quintela <address@hidden 
> <mailto:address@hidden>> wrote:
> 
> 
>     Hi
> 
>     As discussed on this week kvm call, here are the migration tree with
>     XBRLE + huge memory fixes integrated.  There were a bug on huge memory
>     (corrected on the v3 version just sent) and another on XZBRLE patches.
>     Orit is going to resend patches addressing comments, but here the fix is
>     integrated already.
> 
>     How to test?
> 
>     Compile qemu with trace support:
> 
>     ./configure --enable-trace-backend=simple
> 
>     Create an event file:
> 
>     $ cat /tmp/events
>     savevm_section_start
>     savevm_section_end
>     $
> 
>     Now launch qemu with normal command line:
> 
>     qemu ..... --trace events=/tmp/events
> 
>     And when execution finish, you can use a script like the following to
>     see the stalls that happen:
> 
>     $ cat ~/counter_simpletrace
>     $1 ~ /savevm_section_end/ {
>            /* Print savevm_section_stop line when >100 ms duration */
>            if ($2 > 50000) {
>                    printf("%s times_missing=%u\n", $0, times_missing++);
>            }
>     }
>     $
> 
>     And now you can analize:
> 
>     ./scripts/simpletrace.py ./trace-events trace-32554 | awk -f 
> ~/counter_simpletrace
> 
>     (adjust paths as required)
> 
>     Notice that this are stalls on the iothread.  vcpus stalls can still be
>     bigger.  The number that is tested here is 50ms, so I get cases that are
>     a bit bigger (between 60-100ms with one 8GB guest that is dirtying 512MB
>     in a loop.
> 
>     If you get stalls, or drop connections, please let me know the load.
> 
>     Thanks, Juan.
> 
> 
>     The following changes since commit 
> 47ecbdf07ed2c37bdfd2d77137d01bb319ce13da:
> 
>      libcacard: build fixes (2012-06-21 20:04:24 +0000)
> 
>     are available in the git repository at:
> 
>      http://repo.or.cz/r/qemu/quintela.git migration-next
> 
>     for you to fetch changes up to 0844b46b5d7d8d6fa01134d170b3c48b7f32eab7:
> 
>      Add XBZRLE statistics (2012-06-22 15:24:15 +0200)
> 
> 
> Currently this XBZRLE related stats are only available during the active 
> migration but not
> after the completion. Can we get this information even after the completion 
> of the XBZRLE migration (via info migrate) ? It would help to keep track of 
> the final list of cache misses/hits etc.
> 
Sure , I will add it in the next patch set.

> To the generic migration statistics that gets displayed via "info migrate" 
> can you pl. consider adding the duration of Stage3 (i.e. "Downtime") as 
> measured on the source host (yes there is probably some time spent in the 
> resuming of the guest on the destination host...).  
> 
> Ideally this "Downtime" should be the pretty close to the pre-defined 
> downtime (i.e. default value(30ms?) or whatever the user set it to via 
> migrate_set_downtime command). But it looks like on larger guests that is not 
> the case...
> 
> Still reviewing the code and testing it out...
> 
> Thanks
> Vinod
> 
>  
> 
> 
>     ----------------------------------------------------------------
>     Isaku Yamahata (1):
>          Add MigrationParams structure
> 
>     Juan Quintela (8):
>          Add spent time for migration
>          Add tracepoints for savevm section start/end
>          No need to iterate if we already are over the limit
>          Only TCG needs TLB handling
>          Only calculate expected_time for stage 2
>          Exit loop if we have been there too long
>          dirty bitmap: abstract its use
>          Maintain the number of dirty pages
> 
>     Orit Wasserman (13):
>          Add missing check for host_from_stream_offset return value for 
> RAM_SAVE_FLAG_PAGE
>          Add migration capabilites
>          Add XBZRLE documentation
>          Add cache handling functions
>          Add uleb encoding/decoding functions
>          Add save_block_hdr function
>          Add debugging infrastructure
>          Change ram_save_block to return -1 if there are no more changes
>          Add migration_end function
>          Add xbzrle_encode_buffer and xbzrle_decode_buffer functions
>          Add XBZRLE to ram_save_block and ram_save_live
>          Add set_cachesize command
>          Add XBZRLE statistics
> 
>      Makefile.objs        |    1 +
>      arch_init.c          |  378 
> ++++++++++++++++++++++++++++++++++++++++++++------
>      block-migration.c    |    8 +-
>      cache.c              |  219 +++++++++++++++++++++++++++++
>      cpu-all.h            |    1 +
>      cutils.c             |   29 ++++
>      docs/xbzrle.txt      |  115 +++++++++++++++
>      exec-obsolete.h      |   50 ++++---
>      exec.c               |   34 +++--
>      hmp-commands.hx      |   34 +++++
>      hmp.c                |   90 ++++++++++++
>      hmp.h                |    3 +
>      include/qemu/cache.h |   81 +++++++++++
>      migration.c          |  131 +++++++++++++++--
>      migration.h          |   30 +++-
>      monitor.c            |    7 +
>      qapi-schema.json     |   97 ++++++++++++-
>      qemu-common.h        |   19 +++
>      qmp-commands.hx      |   99 +++++++++++++
>      savevm.c             |  115 ++++++++++++++-
>      sysemu.h             |    3 +-
>      trace-events         |    5 +
>      vmstate.h            |    2 +-
>      23 files changed, 1449 insertions(+), 102 deletions(-)
>      create mode 100644 cache.c
>      create mode 100644 docs/xbzrle.txt
>      create mode 100644 include/qemu/cache.h
> 
>