[PATCH v4 0/7] Multifd Migration Compression

[Juan Quintela <quintela@redhat.com>]

Based-on: 20200127223321.2742-1-quintela@redhat.com

[v4]
- create new parameters: multifd-zlib-level & multifd-zstd-level
- use proper "conditionals" for qapi (thanks markus)
- more than half of the patches moved to the migration PULL request
  that this series are based on
- method type has moved to one int from a set of flags
- fixed all reviews comments

Please review.

[v3]
- rebased on top of upstream + previous multifd cancel series
- split multifd code into its own file (multifd.[ch])
- split zstd/zlib compression methods (multifd-zstd/zlib.c)
- use qemu module feauture to avoid ifdefs
  (my understanding is that zlib needs to be present, but
  we setup zstd only if it is not there or is disabled)
- multifd-method: none|zlib|zstd

  As far as I can see, there is no easy way to convince qapi that zstd
  option could/couldn't be there depending on compliation flags. I
  ended just checking in migrate_parameters_check() if it is enabled
  and giving an error message otherwise.

Questions:
- I am "reusing" the compress-level parameter for both zstd and zlib,
  but it poses a problem:
  * zlib values: 1-9 (default: 6?)
  * zstd values: 1-19 (default: 3)
So, what should I do:
  * create multifd-zstd-level and multifd-zlib-level (easier)
  * reuse compress-level, and change its maximum values depending on
    multifd-method
  * any other good option?

Please, review.

[v2] - rebase on top of previous arguments posted to the list -
introduces zlib compression - introduces zstd compression

Please help if you know anything about zstd/zlib compression.

This puts compression on top of multifd. Advantages about current
compression:

- We copy all pages in a single packet and then compress the whole
  thing.

- We reuse the compression stream for all the packets sent through the
  same channel.

- We can select nocomp/zlib/zstd levels of compression.

Please, review.

Juan Quintela (7):
  migration: Add support for modules
  multifd: Make no compression operations into its own structure
  multifd: Add multifd-zlib-level parameter
  multifd: Add zlib compression multifd support
  configure: Enable test and libs for zstd
  multifd: Add multifd-zstd-level parameter
  multifd: Add zstd compression multifd support

 configure                    |  30 ++++
 hw/core/qdev-properties.c    |   2 +-
 include/qemu/module.h        |   2 +
 migration/Makefile.objs      |   2 +
 migration/migration.c        |  57 +++++++
 migration/migration.h        |   3 +
 migration/multifd-zlib.c     | 293 +++++++++++++++++++++++++++++++++
 migration/multifd-zstd.c     | 305 +++++++++++++++++++++++++++++++++++
 migration/multifd.c          | 191 +++++++++++++++++++++-
 migration/multifd.h          |  29 ++++
 migration/ram.c              |   2 +-
 monitor/hmp-cmds.c           |   8 +
 qapi/migration.json          |  58 ++++++-
 tests/qtest/migration-test.c |  16 ++
 vl.c                         |   1 +
 15 files changed, 985 insertions(+), 14 deletions(-)
 create mode 100644 migration/multifd-zlib.c
 create mode 100644 migration/multifd-zstd.c

-- 
2.24.1