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

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Hi,
  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>
  migrate_start_postcopy

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 finished
  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 path
  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
separately.

Current TODO:
   1) It's not bisectable yet
   2) There are no testsuite additions (although I have a virt-test modification
      I've been using).
   3) End-of-migration cleanup is much better than it was but still needs some work.
   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 investigation
      (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.
Dave

Dr. David Alan Gilbert (43):
  qemu_ram_foreach_block: pass up error value, and down the ramblock
    name
  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
    userfault
  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
  qemu_ram_block_from_host
  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

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1.9.3