On 20/01/2017 17:43, Paolo Bonzini wrote: > This series pushes down aio_context_acquire/release to the point > where we can actually reason on using different fine-grained mutexes. > > The main infrastructure is introduced in patch 1. The new API aio_co_wake > starts a coroutine with aio_context_acquire/release protection, which > requires tracking each coroutine's "home" AioContext. aio_co_schedule > instead takes care of moving a sleeping coroutine to a different > AioContext, also ensuring that it runs under aio_context_acquire/release. > This is useful to implement bdrv_set_aio_context, as a simpler alternative > to bottom halves. Even though one-shot BHs are already simpler than > what we had before, after this patch aio_co_wake and aio_co_schedule > save you from having to do aio_context_acquire/release explicitly. > > After patch 2 to 4, which are just small preparatory changes, patches > 5 to 8 provide an example of how to use the new API. In particular patch > 5 to 7 implement a new organization of coroutines in the NBD client, > which allows not blocking on partial reply header reads. > > Patch 9 introduces helpers for AioContext locking in QED, which is > the most complex AIO-based driver left. Then the actual meat of the > series runs from patch 10 to patch 14, followed by small optimizations > in patches 15 and 16. > > The patches do some back and forth in adding/removing > aio_context_acquire/release calls in block/*.c but ultimately a small > number of aio_context_acquire/release pairs are added after the pushdown. > These are mostly in drivers that use external libraries (and actually > they could already be replaced by QemuMutex) and in device models > that support multithreaded operation (aka iothread aka dataplane). > > Notably, coroutines need not care about aio_context_acquire/release. > The device models ensure that the first creation of the coroutine has > the AioContext, while aio_co_wake/aio_co_schedule do the same after > they yield. Therefore, most of the files only need to use those two > functions instead of, respectively, qemu_coroutine_enter and > aio_bh_schedule_oneshot. > > However, this is only an intermediate step which is needed because the > block layer and qemu-coroutine locks are thread-unsafe. So the next > part will add separate locking, independent of AioContext, to block.c and > mostly block/io.c---this includes making CoMutex thread-safe. Patch 17 > therefore already documents the current locking policies block.h to > prepare for the next series. > > Paolo > > v1->v2: > new patch (4) removing block-obj-y -> io-obj-y dependency > removed QIOChannelRestart from > "io: add methods to set I/O handlers on AioContext" > improved qio_channel_set_aio_context docs, renamed to > qio_channel_attach_aio_context > fixed pasto in "io: make qio_channel_yield aware of AioContexts" > document restrictions in bdrv_aio_cancel due to qemu_aio_ref > converted NBD server to qio_channel_yield too > allow NULL s->read_reply_co > > *** BLURB HERE *** > > Paolo Bonzini (17): > aio: introduce aio_co_schedule and aio_co_wake > block-backend: allow blk_prw from coroutine context > test-thread-pool: use generic AioContext infrastructure > block: move AioContext and QEMUTimer to libqemuutil > io: add methods to set I/O handlers on AioContext > io: make qio_channel_yield aware of AioContexts > nbd: convert to use qio_channel_yield > coroutine-lock: reschedule coroutine on the AioContext it was running > on > qed: introduce qed_aio_start_io and qed_aio_next_io_cb > aio: push aio_context_acquire/release down to dispatching > block: explicitly acquire aiocontext in timers that need it > block: explicitly acquire aiocontext in callbacks that need it > block: explicitly acquire aiocontext in bottom halves that need it > block: explicitly acquire aiocontext in aio callbacks that need it > aio-posix: partially inline aio_dispatch into aio_poll > async: remove unnecessary inc/dec pairs > block: document fields protected by AioContext lock > > Makefile.objs | 5 +- > block/blkdebug.c | 9 +- > block/blkreplay.c | 2 +- > block/block-backend.c | 13 ++- > block/curl.c | 44 ++++++-- > block/gluster.c | 9 +- > block/io.c | 38 ++----- > block/iscsi.c | 15 ++- > block/linux-aio.c | 10 +- > block/mirror.c | 12 +- > block/nbd-client.c | 108 ++++++++---------- > block/nbd-client.h | 2 +- > block/nfs.c | 9 +- > block/qed-cluster.c | 2 + > block/qed-table.c | 12 +- > block/qed.c | 58 +++++++--- > block/qed.h | 3 + > block/sheepdog.c | 29 ++--- > block/ssh.c | 29 ++--- > block/throttle-groups.c | 2 + > block/win32-aio.c | 9 +- > dma-helpers.c | 2 + > hw/block/virtio-blk.c | 19 +++- > hw/scsi/scsi-bus.c | 2 + > hw/scsi/scsi-disk.c | 15 +++ > hw/scsi/scsi-generic.c | 20 +++- > hw/scsi/virtio-scsi.c | 6 + > include/block/aio.h | 38 ++++++- > include/block/block_int.h | 64 ++++++----- > include/io/channel.h | 72 +++++++++++- > include/qemu/coroutine_int.h | 10 +- > include/sysemu/block-backend.h | 14 ++- > io/channel-command.c | 13 +++ > io/channel-file.c | 11 ++ > io/channel-socket.c | 16 ++- > io/channel-tls.c | 12 ++ > io/channel-watch.c | 6 + > io/channel.c | 97 ++++++++++++---- > nbd/client.c | 2 +- > nbd/common.c | 9 +- > nbd/server.c | 94 +++++----------- > stubs/Makefile.objs | 2 + > stubs/linux-aio.c | 32 ++++++ > stubs/main-loop.c | 8 ++ > stubs/set-fd-handler.c | 11 -- > tests/Makefile.include | 18 +-- > tests/iothread.c | 91 +++++++++++++++ > tests/iothread.h | 25 +++++ > tests/test-aio-multithread.c | 213 > ++++++++++++++++++++++++++++++++++++ > tests/test-thread-pool.c | 12 +- > tests/test-vmstate.c | 11 -- > trace-events | 4 + > util/Makefile.objs | 5 +- > aio-posix.c => util/aio-posix.c | 60 +++------- > aio-win32.c => util/aio-win32.c | 30 ++--- > util/aiocb.c | 55 ++++++++++ > async.c => util/async.c | 84 ++++++++++++-- > util/qemu-coroutine-lock.c | 5 +- > util/qemu-coroutine-sleep.c | 2 +- > util/qemu-coroutine.c | 8 ++ > qemu-timer.c => util/qemu-timer.c | 0 > thread-pool.c => util/thread-pool.c | 6 +- > util/trace-events | 1 - > 63 files changed, 1155 insertions(+), 465 deletions(-) > create mode 100644 stubs/linux-aio.c > create mode 100644 stubs/main-loop.c > create mode 100644 tests/iothread.c > create mode 100644 tests/iothread.h > create mode 100644 tests/test-aio-multithread.c > rename aio-posix.c => util/aio-posix.c (94%) > rename aio-win32.c => util/aio-win32.c (95%) > create mode 100644 util/aiocb.c > rename async.c => util/async.c (82%) > rename qemu-timer.c => util/qemu-timer.c (100%) > rename thread-pool.c => util/thread-pool.c (98%) >
Ping? Paolo
