Re: [PATCH v6 0/3] util/thread-pool: Expose minimun and maximum size

[Stefan Hajnoczi]

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

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