On Wed, Sep 13, 2023 at 04:00:41PM -0400, Stefan Hajnoczi wrote:
> v3:
> - Add comment pointing to API documentation in .c file [Philippe]
> - Add virtio_notify_irqfd_deferred_fn trace event [Ilya]
> - Remove outdated #include [Ilya]
> v2:
> - Rename blk_io_plug() to defer_call() and move it to util/ so the net
> subsystem can use it [Ilya]
> - Add defer_call_begin()/end() to thread_pool_completion_bh() to match Linux
> AIO and io_uring completion batching
>
> Replace the seldom-used virtio-blk notification BH mechanism with
> blk_io_plug(). This is part of an effort to enable the multi-queue block layer
> in virtio-blk. The notification BH was not multi-queue friendly.
>
> The blk_io_plug() mechanism improves fio rw=randread bs=4k iodepth=64 numjobs=8
> IOPS by ~9% with a single IOThread and 8 vCPUs (this is not even a multi-queue
> block layer configuration) compared to no completion batching. iodepth=1
> decreases by ~1% but this could be noise. Benchmark details are available here:
> https://gitlab.com/stefanha/virt-playbooks/-/tree/blk_io_plug-irqfd
virtio things:
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
regression is a bit worrysome if real though - just do a bit
longer testing to make sure?
> Stefan Hajnoczi (4):
> block: rename blk_io_plug_call() API to defer_call()
> util/defer-call: move defer_call() to util/
> virtio: use defer_call() in virtio_irqfd_notify()
> virtio-blk: remove batch notification BH
>
> MAINTAINERS | 3 +-
> include/qemu/defer-call.h | 16 +++
> include/sysemu/block-backend-io.h | 4 -
> block/blkio.c | 9 +-
> block/io_uring.c | 11 ++-
> block/linux-aio.c | 9 +-
> block/nvme.c | 5 +-
> block/plug.c | 159 ------------------------------
> hw/block/dataplane/virtio-blk.c | 48 +--------
> hw/block/dataplane/xen-block.c | 11 ++-
> hw/block/virtio-blk.c | 5 +-
> hw/scsi/virtio-scsi.c | 7 +-
> hw/virtio/virtio.c | 13 ++-
> util/defer-call.c | 156 +++++++++++++++++++++++++++++
> util/thread-pool.c | 5 +
> block/meson.build | 1 -
> hw/virtio/trace-events | 1 +
> util/meson.build | 1 +
> 18 files changed, 231 insertions(+), 233 deletions(-)
> create mode 100644 include/qemu/defer-call.h
> delete mode 100644 block/plug.c
> create mode 100644 util/defer-call.c
>
> --
> 2.41.0