[Qemu-devel] [PATCH v2 0/5] migration: improve multithreads

[guangrong . xiao]

From: Xiao Guangrong <address@hidden>

Changelog in v2:
These changes are based on Paolo's suggestion:
1) rename the lockless multithreads model to threaded workqueue
2) hugely improve the internal design, that make all the request be
   a large array, properly partition it, assign requests to threads
   respectively and use bitmaps to sync up threads and the submitter,
   after that ptr_ring and spinlock are dropped
3) introduce event wait for the submitter

These changes are based on Emilio's review:
4) make more detailed description for threaded workqueue
5) add a benchmark for threaded workqueue

The previous version can be found at
        https://marc.info/?l=kvm&m=153968821910007&w=2

There's the simple performance measurement comparing these two versions,
the environment is the same as we listed in the previous version.

Use 8 threads to compress the data in the source QEMU
- with compress-wait-thread = off


      total time        busy-ratio
--------------------------------------------------
v1    125066            0.38
v2    120444            0.35

- with compress-wait-thread = on
         total time    busy-ratio
--------------------------------------------------
v1    164426            0
v2    142609            0

The v2 win slightly.

Xiao Guangrong (5):
  bitops: introduce change_bit_atomic
  util: introduce threaded workqueue
  migration: use threaded workqueue for compression
  migration: use threaded workqueue for decompression
  tests: add threaded-workqueue-bench

 include/qemu/bitops.h             |  13 +
 include/qemu/threaded-workqueue.h |  94 +++++++
 migration/ram.c                   | 538 ++++++++++++++------------------------
 tests/Makefile.include            |   5 +-
 tests/threaded-workqueue-bench.c  | 256 ++++++++++++++++++
 util/Makefile.objs                |   1 +
 util/threaded-workqueue.c         | 466 +++++++++++++++++++++++++++++++++
 7 files changed, 1030 insertions(+), 343 deletions(-)
 create mode 100644 include/qemu/threaded-workqueue.h
 create mode 100644 tests/threaded-workqueue-bench.c
 create mode 100644 util/threaded-workqueue.c

-- 
2.14.5