On Tue, Feb 3, 2026 at 5:52 PM Michael S. Tsirkin <[email protected]> wrote: > > On Sat, Nov 15, 2025 at 12:08:07PM +0200, Manos Pitsidianakis wrote: > > On Fri, Nov 14, 2025 at 11:35 AM Yanfeng Liu <[email protected]> wrote: > > > > > > Media players needs meaningful latency_bytes update but it is > > > zero now most of the time. This adds stream-wise latency_bytes > > > calculation so that to improve the situation. > > > > > > Signed-off-by: Yanfeng Liu <[email protected]> > > > --- > > Manos what do you want to do with this patch? >
If it indeed fixes performance then the changes LGTM. Reviewed-by: Manos Pitsidianakis <[email protected]> Michael, could you pick up this patch in your maintainer pull request? > > > > Thanks for this patch. The virtio spec doesn't adequately explain what > > latency_bytes means, could you explain what it does and why it's > > needed? And also what behavior in media players this patch fixes? > > > > Thanks again! > > > > > hw/audio/virtio-snd.c | 12 +++++++++++- > > > include/hw/audio/virtio-snd.h | 1 + > > > 2 files changed, 12 insertions(+), 1 deletion(-) > > > > > > diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c > > > index 9101560f38..ed0422b45a 100644 > > > --- a/hw/audio/virtio-snd.c > > > +++ b/hw/audio/virtio-snd.c > > > @@ -431,6 +431,7 @@ static uint32_t virtio_snd_pcm_prepare(VirtIOSound > > > *s, uint32_t stream_id) > > > stream->id = stream_id; > > > stream->pcm = s->pcm; > > > stream->s = s; > > > + stream->latency_bytes = 0; > > > qemu_mutex_init(&stream->queue_mutex); > > > QSIMPLEQ_INIT(&stream->queue); > > > > > > @@ -899,6 +900,7 @@ static void virtio_snd_handle_tx_xfer(VirtIODevice > > > *vdev, VirtQueue *vq) > > > buffer->vq = vq; > > > buffer->size = size; > > > buffer->offset = 0; > > > + stream->latency_bytes += size; > > > > > > QSIMPLEQ_INSERT_TAIL(&stream->queue, buffer, entry); > > > } > > > @@ -1112,12 +1114,19 @@ error_cleanup: > > > virtio_snd_unrealize(dev); > > > } > > > > > > +static inline void update_latency(VirtIOSoundPCMStream *s, size_t used) > > > +{ > > > + s->latency_bytes = s->latency_bytes > used ? > > > + s->latency_bytes - used : 0; > > > +} > > > + > > > static inline void return_tx_buffer(VirtIOSoundPCMStream *stream, > > > VirtIOSoundPCMBuffer *buffer) > > > { > > > virtio_snd_pcm_status resp = { 0 }; > > > resp.status = cpu_to_le32(VIRTIO_SND_S_OK); > > > - resp.latency_bytes = cpu_to_le32((uint32_t)buffer->size); > > > + update_latency(stream, buffer->size); > > > + resp.latency_bytes = cpu_to_le32(stream->latency_bytes); > > > iov_from_buf(buffer->elem->in_sg, > > > buffer->elem->in_num, > > > 0, > > > @@ -1178,6 +1187,7 @@ static void virtio_snd_pcm_out_cb(void *data, int > > > available) > > > buffer->size -= size; > > > buffer->offset += size; > > > available -= size; > > > + update_latency(stream, size); > > > if (buffer->size < 1) { > > > return_tx_buffer(stream, buffer); > > > break; > > > diff --git a/include/hw/audio/virtio-snd.h b/include/hw/audio/virtio-snd.h > > > index c176066584..9560bac8b1 100644 > > > --- a/include/hw/audio/virtio-snd.h > > > +++ b/include/hw/audio/virtio-snd.h > > > @@ -150,6 +150,7 @@ struct VirtIOSoundPCMStream { > > > } voice; > > > QemuMutex queue_mutex; > > > bool active; > > > + uint32_t latency_bytes; > > > QSIMPLEQ_HEAD(, VirtIOSoundPCMBuffer) queue; > > > }; > > > > > > -- > > > 2.34.1 > > > > -- Manos Pitsidianakis Emulation and Virtualization Engineer at Linaro Ltd
