[PATCH v4 0/3] Zero copy improvements (QIOChannel + multifd)

[Leonardo Bras]

The first patch avoid spuriously returning 1 [*] when zero-copy flush is
attempted before any buffer was sent using MSG_ZEROCOPY.

[*] zero-copy not being used, even though it's enabled and supported
by kernel

The second patch introduces a new migration stat
(dirty-sync-missed-zero-copy) that will be used to keep track of [*]. 

The third patch keeps track of how many zero-copy flushes retured 1 [*]

Changes since v3:
- Patch#1: Also checks if no packet was queued after the last flush
- Patch#2: Improve dirty-sync-missed-zero-copy doc and hmp print message

Changes since v2:
- Documentation release number changed from 7.2 to 7.1
- migration stat renamed from zero-copy-copied to 
  dirty-sync-missed-zero-copy
- Updated documentation to make it more user-friendly

Changes since v1:
- Idea of using a warning replaced by using a migration stat counter



Leonardo Bras (3):
  QIOChannelSocket: Fix zero-copy flush returning code 1 when nothing
    sent
  Add dirty-sync-missed-zero-copy migration stat
  migration/multifd: Report to user when zerocopy not working

 qapi/migration.json   | 7 ++++++-
 migration/ram.h       | 2 ++
 io/channel-socket.c   | 8 +++++++-
 migration/migration.c | 2 ++
 migration/multifd.c   | 2 ++
 migration/ram.c       | 5 +++++
 monitor/hmp-cmds.c    | 5 +++++
 7 files changed, 29 insertions(+), 2 deletions(-)

-- 
2.37.0