This patch series intends to enable MSG_ZEROCOPY in QIOChannel, and make
use of it for multifd migration performance improvement.
Patch #1 creates new callbacks for QIOChannel, allowing the implementation
of zerocopy writing.
Patch #2 implements writev_zerocopy and flush_zerocopy on QIOChannelSocket,
making use of MSG_ZEROCOPY on Linux.
Patch #3 Makes use of QIOChannelSocket zerocopy implementation on
nocomp multifd migration.
Results:
So far, the resource usage of __sys_sendmsg() reduced 15 times, and the
overall migration took 13-22% less time, based in synthetic workload.
The objective is to reduce migration time in hosts with heavy cpu usage.
---
Changes since v3:
- QIOChannel interface names changed from io_async_{writev,flush} to
io_{writev,flush}_zerocopy
- Instead of falling back in case zerocopy is not implemented, return
error and abort operation.
- Flush now waits as long as needed, or return error in case anything
goes wrong, aborting the operation.
- Zerocopy is now conditional in multifd, being set by parameter
multifd-zerocopy
- Moves zerocopy_flush to multifd_send_sync_main() from multifd_save_cleanup
so migration can abort if flush goes wrong.
- Several other small improvements
Changes since v2:
- Patch #1: One more fallback
- Patch #2: Fall back to sync if fails to lock buffer memory in MSG_ZEROCOPY
send.
Changes since v1:
- Reimplemented the patchset using async_write + async_flush approach.
- Implemented a flush to be able to tell whenever all data was written.
Leonardo Bras (3):
QIOChannel: Add io_writev_zerocopy & io_flush_zerocopy callbacks
QIOChannelSocket: Implement io_writev_zerocopy & io_flush_zerocopy for
CONFIG_LINUX
multifd: Implement zerocopy write in multifd migration
(multifd-zerocopy)
qapi/migration.json | 18 ++++
include/io/channel-socket.h | 2 +
include/io/channel.h | 104 +++++++++++++++++----
migration/migration.h | 1 +
migration/multifd.h | 2 +-
io/channel-socket.c | 180 ++++++++++++++++++++++++++++++++++--
io/channel.c | 74 +++++++++++----
migration/migration.c | 20 ++++
migration/multifd.c | 33 ++++++-
migration/ram.c | 20 ++--
monitor/hmp-cmds.c | 4 +
11 files changed, 399 insertions(+), 59 deletions(-)
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2.33.0
