On Mon, Apr 25, 2022 at 09:57:20AM +0200, Nicolas Saenz Julienne wrote:
> As discussed on the previous RFC[1] the thread-pool's dynamic thread
> management doesn't play well with real-time and latency sensitive
> systems. This series introduces a set of controls that'll permit
> achieving more deterministic behaviours, for example by fixing the
> pool's size.
>
> We first introduce a new common interface to event loop configuration by
> moving iothread's already available properties into an abstract class
> called 'EventLooopBackend' and have both 'IOThread' and the newly
> created 'MainLoop' inherit the properties from that class.
>
> With this new configuration interface in place it's relatively simple to
> introduce new options to fix the even loop's thread pool sizes. The
> resulting QAPI looks like this:
>
> -object main-loop,id=main-loop,thread-pool-min=1,thread-pool-max=1
>
> Note that all patches are bisect friendly and pass all the tests.
>
> [1] https://patchwork.ozlabs.org/project/qemu-devel/patch/20220202175234.656711-1-nsaenzju@redhat.com/
> ---
>
> Changes since v5:
> - Add 'Since' versioning to MainLoopProperties
>
> Changes since v4:
> - Address Markus' comments WRT qom.json
>
> Changes since v3:
> - Avoid duplication in qom.json by creating EventLoopBaseProperties.
> - Fix failures on first compilation due to race between
> event-loop-base.o and qapi header generation.
>
> Changes since v2:
> - Get rid of wrong locking/waiting
> - Fix qapi versioning
> - Better commit messages
>
> Changes since v1:
> - Address all Stefan's comments
> - Introduce new fix
>
> Nicolas Saenz Julienne (3):
> Introduce event-loop-base abstract class
> util/main-loop: Introduce the main loop into QOM
> util/event-loop-base: Introduce options to set the thread pool size
>
> event-loop-base.c | 140 +++++++++++++++++++++++++++++++
> include/block/aio.h | 10 +++
> include/block/thread-pool.h | 3 +
> include/qemu/main-loop.h | 10 +++
> include/sysemu/event-loop-base.h | 41 +++++++++
> include/sysemu/iothread.h | 6 +-
> iothread.c | 68 +++++----------
> meson.build | 26 +++---
> qapi/qom.json | 43 ++++++++--
> util/aio-posix.c | 1 +
> util/async.c | 20 +++++
> util/main-loop.c | 65 ++++++++++++++
> util/thread-pool.c | 55 +++++++++++-
> 13 files changed, 419 insertions(+), 69 deletions(-)
> create mode 100644 event-loop-base.c
> create mode 100644 include/sysemu/event-loop-base.h
>
> --
> 2.35.1
>
Thanks, applied to my block-next tree! If there are more comments I can
drop it again.
https://gitlab.com/stefanha/qemu/commits/block-next
Stefan