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Re: [Qemu-devel] [PATCH v2 00/43] Postcopy implementation

From: zhanghailiang
Subject: Re: [Qemu-devel] [PATCH v2 00/43] Postcopy implementation
Date: Tue, 12 Aug 2014 09:50:34 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1

On 2014/8/11 22:29, Dr. David Alan Gilbert (git) wrote:
From: "Dr. David Alan Gilbert"<address@hidden>

   This is a 2nd cut of my postcopy implementation; it fixes up some
of the comments from the 1st posting but it also fixes a lot of bugs,
(other comments from the 1st round will be fixed later).

The commands to start a postcopy migration have changed to:

   migrate_set_capability x-postcopy-ram on
   migrate -d   tcp:whereever
   <some time later>

Starting the destination in paused mode (-s) now works.

This now survives in a test harness with a few hundred migrations without
problems (both on heavily loaded and idle VMs).

Other changes:
   Changed source rp handler to coroutine (from fd_set_handler) - cures
     occasional loss of requests (and hence huge latency spikes)
   Added 'SHUT' rp command as a handshake from the destination that it's 
   Fixed race during migration of guest with very little page modification
   Shutdown the fault-thread cleanly
   Update 'received' map in ADVISE state
   Turned off nagling on rp - we want our requests to get their ASAP
   Fixed seg when attempting to postcopy to a stream that couldn't get a return 
   Got rid of the move of QEMUFile into the .h
   Fixed up '-ve' and title of assert patch
   Removed a couple of return-path opening optimisations as per Paolo's comments

Note this version needs the QEMUSizedBuffer/QEMUFile patches that I've posted

Current TODO:
    1) It's not bisectable yet
    2) There are no testsuite additions (although I have a virt-test 
       I've been using).
    3) End-of-migration cleanup is much better than it was but still needs some 
    4) Not all the code is there for systems with hostpagesize!=qemupagesize
    5) xbzrle needs disabling once in postcopy
    6) RDMA needs some rework
    7) The latency measurements are now pretty consistent, no very large spikes,
       but they're a bit higher than expected, I need to look at rate limiting
       just the background scan.
    8) Conversion of return-path to a process and blocking fd needs 
       (as per discussion with Paolo)
    9) Andrea has suggestions on ways to avoid some of the huge-page splitting
       that occurs during the discard phase after precopy.
   10) I'd like to format the data on the return path in a more structured way
       (i.e. maybe using stuff from my BER world).
   11) The ACPI fix in 2.1 that allowed migrating RAMBlocks to be larger than
       the source feels like it needs looking at for postcopy.

Dr. David Alan Gilbert (43):
   qemu_ram_foreach_block: pass up error value, and down the ramblock
   improve DPRINTF macros, add to savevm
   Add qemu_get_counted_string to read a string prefixed by a count byte
   Create MigrationIncomingState

   Return path: socket_writev_buffer: Block even on non-blocking fd's
   Migration commands
   Return path: Control commands
   Return path: Send responses from destination to source
   Return path: Source handling of return path
   qemu_loadvm errors and debug
   ram_debug_dump_bitmap: Dump a migration bitmap as text
   Rework loadvm path for subloops
   Add migration-capability boolean for postcopy-ram.
   Add wrappers and handlers for sending/receiving the postcopy-ram
     migration messages.
   QEMU_VM_CMD_PACKAGED: Send a packaged chunk of migration stream
   migrate_init: Call from savevm
   Allow savevm handlers to state whether they could go into postcopy
   postcopy: OS support test
   migrate_start_postcopy: Command to trigger transition to postcopy
   MIG_STATE_POSTCOPY_ACTIVE: Add new migration state
   qemu_savevm_state_complete: Postcopy changes
   Postcopy: Maintain sentmap during postcopy pre phase
   Postcopy page-map-incoming (PMI) structure
   postcopy: Add incoming_init/cleanup functions
   postcopy: Incoming initialisation
   postcopy: ram_enable_notify to switch on userfault
   Postcopy: postcopy_start
   Postcopy: Rework migration thread for postcopy mode
   mig fd_connect: open return path
   Postcopy: Create a fault handler thread before marking the ram as
   Page request:  Add MIG_RPCOMM_REQPAGES reverse command
   Page request: Process incoming page request
   Page request: Consume pages off the post-copy queue
   Add assertion to check migration_dirty_pages
   postcopy_ram.c: place_page and helpers
   Postcopy: Use helpers to map pages during migration
   Postcopy; Handle userfault requests
   Start up a postcopy/listener thread ready for incoming page data
   postcopy: Wire up loadvm_postcopy_ram_handle_{run,end} commands
   End of migration for postcopy
   Start documenting how postcopy works.

  Makefile.objs                    |   2 +-
  arch_init.c                      | 490 +++++++++++++++++++--
  docs/migration.txt               | 150 +++++++
  exec.c                           |  66 ++-
  hmp-commands.hx                  |  15 +
  hmp.c                            |   7 +
  hmp.h                            |   1 +
  include/exec/cpu-common.h        |   8 +-
  include/migration/migration.h    | 128 ++++++
  include/migration/postcopy-ram.h |  89 ++++
  include/migration/qemu-file.h    |   9 +
  include/migration/vmstate.h      |   2 +-
  include/qemu/typedefs.h          |   7 +-
  include/sysemu/sysemu.h          |  41 +-
  migration-rdma.c                 |   4 +-
  migration.c                      | 667 ++++++++++++++++++++++++++--
  postcopy-ram.c                   | 915 +++++++++++++++++++++++++++++++++++++++
  qapi-schema.json                 |  14 +-
  qemu-file.c                      | 124 +++++-
  qmp-commands.hx                  |  19 +
  savevm.c                         | 854 +++++++++++++++++++++++++++++++++---
  21 files changed, 3473 insertions(+), 139 deletions(-)
  create mode 100644 include/migration/postcopy-ram.h
  create mode 100644 postcopy-ram.c

Hi Dave,

I want to test your patches, but i failed to 'git am' them to the new
qemu-2.1 source. I want to know if you has a git-branch which i can
git clone directly? Thanks.

Best regards,

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