This patch series changes the global thread pool to a one ThreadPool per AioContext model. We still only use the main loop AioContext so in practice there is just one ThreadPool. But this opens the door to refactoring the block layer (which depends on ThreadPool) so block devices can be accessed outside the global mutex in the future.
ThreadPool is tightly bound to an AioContext because it uses an EventNotifier to signal work completion. Completed work items are reaped and their callback functions are invoked from the EventNotifier read handler (executing under AioContext). It might be possible to record the AioContext for the completion callback on a per-request basis and continuing to use a global pool of worker threads. After discussing thread pool models with Paolo I have been convinced that it is simpler and more scalable to have one ThreadPool per AioContext instead. Therefore this series implements the 1:1 approach. For details on previous thread pool model discussion, see: http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg03987.html The final patch was previously separate but I have included it because it depends on qemu_get_aio_context(). It is unrelated to ThreadPool but the patch reviewers are the same in both instances, so I combined the series. At the end of this series block/raw-posix.c and block/raw-win32.c are aware of the ThreadPool they submit work to. The next step after this series is to associate BlockDriverState with an AioContext so that the block layer can run outside the global main loop. v2: * Always find AioContext, don't split if (ctx) cases [Paolo] * Introduce bdrv_get_aio_context() [Paolo] * Add CoQueue AioContext patch since it depends on qemu_get_aio_context() Stefan Hajnoczi (7): main-loop: add qemu_get_aio_context() threadpool: move globals into struct ThreadPool threadpool: add thread_pool_new() and thread_pool_free() aio: add a ThreadPool instance to AioContext block: add bdrv_get_aio_context() threadpool: drop global thread pool coroutine: use AioContext for CoQueue BH async.c | 11 ++ block.c | 6 ++ block/raw-posix.c | 8 +- block/raw-win32.c | 4 +- include/block/aio.h | 6 ++ include/block/block_int.h | 7 ++ include/block/coroutine.h | 1 + include/block/thread-pool.h | 15 ++- include/qemu/main-loop.h | 5 + main-loop.c | 5 + qemu-coroutine-lock.c | 55 ++++++---- tests/test-thread-pool.c | 44 ++++---- thread-pool.c | 243 ++++++++++++++++++++++++++++---------------- trace-events | 4 +- 14 files changed, 276 insertions(+), 138 deletions(-) -- 1.8.1.4