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[Qemu-devel] [PATCH v3 00/47] Postcopy implementation


From: Dr. David Alan Gilbert (git)
Subject: [Qemu-devel] [PATCH v3 00/47] Postcopy implementation
Date: Thu, 28 Aug 2014 16:03:17 +0100

From: "Dr. David Alan Gilbert" <address@hidden>

Hi,
  This is the 3rd cut of my postcopy implementation.  

The two largest changes since V2 are:
    * The source side return path handler is now a thread, and that
      allows the source side fd to be blocking.  (I'm using shutdown(2)
      to make that thread joinable at the end).  I've not changed the
      destination side yet, I'm still concerned that we could end
      up blocking the HMP/QMP if we're not careful.

    * The dirty bitmaps are no longer sync'ed after we switch into postcopy
      We no longer need to do it, because in principal nothing should change,
      and indeed if it does change, the dirtying caused the page to be resent
      and the destination would reject it (as it should since it can have been
      changing itself).  In practice I'm seeing occasional cases where dirtying
      was happening, I'm suspecting this might be related to the networking
      code still being live (see the current patches on the list to stop that)
      but I haven't dug too deep on this.

There are also a bunch of other fixes:
  Docs update (Paolo's comments, and Eric's)
  postcopy test: fix error path (zhanghailiang's comment)
  More clean up of exit cases; a lot less TODO's
  More bisectable - but not there yet

I've also included the QEMUSizedBuffer/QEMUFile patches in this set for those
who want to patch from the mail; but still intend to update them separately.

      
This code is also now in a public GIT repo; see

https://github.com/orbitfp7/qemu/tree/wp3-postcopy

This version is tag: wp3-postcopy-v3 on the wp3-postcopy branch.

Postcopy requires the kernel modifications from Andrea posted here:
  http://lists.gnu.org/archive/html/qemu-devel/2014-07/msg00525.html

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) Not all the code is there for systems with hostpagesize!=qemupagesize
   4) xbzrle needs disabling once in postcopy
   5) RDMA needs some rework
   6) 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.
   7) Conversion of destination side return-path to blocking fd needs 
investigation
      (as per discussion with Paolo)
   8) Andrea has suggestions on ways to avoid some of the huge-page splitting
      that occurs during the discard phase after precopy.
   9) 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).
  10) The ACPI fix in 2.1 that allowed migrating RAMBlocks to be larger than
      the source feels like it needs looking at for postcopy.
  11) I've got an occasional (1/100 ~ 1/500ish) failure on migration of idle VMs

Dave



Dr. David Alan Gilbert (47):
  QEMUSizedBuffer/QEMUFile
  Tests: QEMUSizedBuffer/QEMUBuffer
  Start documenting how postcopy works.
  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
  socket shutdown
  Return path: Open a return path on QEMUFile for sockets
  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
  Don't sync dirty bitmaps in postcopy
  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

 Makefile.objs                    |   2 +-
 arch_init.c                      | 499 +++++++++++++++++++--
 docs/migration.txt               | 188 ++++++++
 exec.c                           |  66 ++-
 hmp-commands.hx                  |  15 +
 hmp.c                            |   7 +
 hmp.h                            |   1 +
 include/exec/cpu-common.h        |   8 +-
 include/migration/migration.h    | 127 ++++++
 include/migration/postcopy-ram.h |  89 ++++
 include/migration/qemu-file.h    |  47 ++
 include/migration/vmstate.h      |   2 +-
 include/qemu/sockets.h           |   1 +
 include/qemu/typedefs.h          |   8 +-
 include/sysemu/sysemu.h          |  41 +-
 migration-rdma.c                 |   4 +-
 migration.c                      | 680 ++++++++++++++++++++++++++--
 postcopy-ram.c                   | 924 +++++++++++++++++++++++++++++++++++++++
 qapi-schema.json                 |  14 +-
 qemu-file.c                      | 552 ++++++++++++++++++++++-
 qmp-commands.hx                  |  19 +
 savevm.c                         | 848 ++++++++++++++++++++++++++++++++---
 tests/Makefile                   |   2 +-
 tests/test-vmstate.c             |  73 ++--
 util/qemu-sockets.c              |  28 ++
 25 files changed, 4069 insertions(+), 176 deletions(-)
 create mode 100644 include/migration/postcopy-ram.h
 create mode 100644 postcopy-ram.c

-- 
1.9.3




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