On Wed, May 14, 2014 at 07:40:18PM +0200, Benoît Canet wrote: > The Wednesday 14 May 2014 à 16:22:44 (+0200), Stefan Hajnoczi wrote : > > This series applies on top of my "dataplane: use QEMU block layer" series. > > > > Now that the dataplane code path is using the QEMU block layer we should > > make > > I/O throttling limits safe to use. When the block_set_io_throttle monitor > > command is executed, the BlockDriverState's AioContext must be acquired in > > order to prevent race conditions with the IOThread that is processing > > requests > > from the guest. > > > > The new block layer AioContext detach/attach mechanism needs to be extended > > to > > move the throttling timer to a new AioContext. This makes throttling work > > across bdrv_set_aio_context() calls. > > > > The result of this series is that I/O throttling works with dataplane and > > limits may be changed at runtime using the monitor. > > > > Stefan Hajnoczi (3): > > throttle: add throttle_detach/attach_aio_context() > > throttle: add detach/attach test case > > blockdev: acquire AioContext in block_set_io_throttle > > > > block.c | 7 +++++++ > > blockdev.c | 6 ++++++ > > include/qemu/throttle.h | 10 ++++++++++ > > tests/test-throttle.c | 49 > > ++++++++++++++++++++++++++++++++++++++++++++----- > > util/throttle.c | 27 +++++++++++++++++++++++---- > > 5 files changed, 90 insertions(+), 9 deletions(-) > > > > -- > > 1.9.0 > > > > I find One thing chocking is this series. > I carefully decloupled the throttling code from the block layer so anyone > could reuse it. > I am under the impression that this series couples it back.
The coupling is just due to the current header file layout. It is not a real coupling to the block layer. Throttling has a dependency on timers. Timers are part of an event loop (either AioContext or main loop). The AioContext prototypes happen to be in block/aio.h but they are not a dependency on block.h or BlockDriverState. This means we could extract them and move them to qemu/aiocontext.h in a separate series. Hope this explains the block/aio.h header and shows it's not true coupling. Stefan
