[PATCH v1 0/3] QIOChannel flags + multifd zerocopy

[Leonardo Bras]

This patch series intends to enable MSG_ZEROCOPY in QIOChannel, and make
use of it for multifd migration performance improvement.

Patch #1 enables the use of flags on qio_channel_write*(), allowing
more flexibility in using the channel. 
It was designed for MSG_ZEROCOPY usage, in which it's a good idea
having a eassy way to choose what packets are sent with the flag, but
also makes it more flexible for future usage.

Patch #2 just adds the MSG_ZEROCOPY feature, and defines the enablement
mechanics, while not enabling it in any code.

Patch #3 enables MSG_ZEROCOPY for migration / multifd.


Results:
So far, the resource usage of __sys_sendmsg() reduced 15 times, and the
overall migration took 13-18% less time, based in synthetic workload.

The objective is to reduce migration time in hosts with heavy cpu usage.

Leonardo Bras (3):
  io: Enable write flags for QIOChannel
  io: Add zerocopy and errqueue
  migration: multifd: Enable zerocopy

 chardev/char-io.c                   |  2 +-
 hw/remote/mpqemu-link.c             |  2 +-
 include/io/channel-socket.h         |  2 +
 include/io/channel.h                | 85 +++++++++++++++++++++++------
 io/channel-buffer.c                 |  1 +
 io/channel-command.c                |  1 +
 io/channel-file.c                   |  1 +
 io/channel-socket.c                 | 80 ++++++++++++++++++++++++++-
 io/channel-tls.c                    | 12 ++++
 io/channel-websock.c                | 10 ++++
 io/channel.c                        | 64 +++++++++++++---------
 migration/multifd-zlib.c            |  7 ++-
 migration/multifd-zstd.c            |  7 ++-
 migration/multifd.c                 |  9 ++-
 migration/multifd.h                 |  3 +-
 migration/rdma.c                    |  1 +
 scsi/pr-manager-helper.c            |  2 +-
 tests/unit/test-io-channel-socket.c |  1 +
 18 files changed, 235 insertions(+), 55 deletions(-)

-- 
2.33.0