* [virtio-comment] [PATCH] virtio-sound: add latency_bytes definition @ 2023-10-05 9:41 Matias Ezequiel Vara Larsen 2023-11-07 10:46 ` [virtio-comment] " Matias Ezequiel Vara Larsen 0 siblings, 1 reply; 6+ messages in thread From: Matias Ezequiel Vara Larsen @ 2023-10-05 9:41 UTC (permalink / raw) To: virtio-comment; +Cc: anton.yakovlev This commit aims at providing a better definition of latency_bytes. To do so, this commit defines latency_bytes as is defined in Crosvm. Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> --- device-types/sound/description.tex | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex index 54c9c8e..1349765 100644 --- a/device-types/sound/description.tex +++ b/device-types/sound/description.tex @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device \begin{description} \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, and VIRTIO_SND_S_IO_ERR otherwise. -\item[\field{latency_bytes}] indicates the current device latency. +\item[\field{latency_bytes}] indicates the current device latency. For +playback, this is the amount of bytes that must be consumed before +the current request can be played. For capture, this is the latency in terms of +bytes that the capture buffer was recorded. \end{description} Since all buffers in the queue (with one exception) should be of the size -- 2.41.0 This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [virtio-comment] Re: [PATCH] virtio-sound: add latency_bytes definition 2023-10-05 9:41 [virtio-comment] [PATCH] virtio-sound: add latency_bytes definition Matias Ezequiel Vara Larsen @ 2023-11-07 10:46 ` Matias Ezequiel Vara Larsen 2023-11-30 1:30 ` Anton Yakovlev 0 siblings, 1 reply; 6+ messages in thread From: Matias Ezequiel Vara Larsen @ 2023-11-07 10:46 UTC (permalink / raw) To: virtio-comment; +Cc: anton.yakovlev Ping Anton. Thanks, Matias. On Thu, Oct 5, 2023 at 11:41 AM Matias Ezequiel Vara Larsen <mvaralar@redhat.com> wrote: > > This commit aims at providing a better definition of latency_bytes. To > do so, this commit defines latency_bytes as is defined in Crosvm. > > Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> > --- > device-types/sound/description.tex | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex > index 54c9c8e..1349765 100644 > --- a/device-types/sound/description.tex > +++ b/device-types/sound/description.tex > @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device > \begin{description} > \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, > and VIRTIO_SND_S_IO_ERR otherwise. > -\item[\field{latency_bytes}] indicates the current device latency. > +\item[\field{latency_bytes}] indicates the current device latency. For > +playback, this is the amount of bytes that must be consumed before > +the current request can be played. For capture, this is the latency in terms of > +bytes that the capture buffer was recorded. > \end{description} > > Since all buffers in the queue (with one exception) should be of the size > -- > 2.41.0 > This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* [virtio-comment] Re: [PATCH] virtio-sound: add latency_bytes definition 2023-11-07 10:46 ` [virtio-comment] " Matias Ezequiel Vara Larsen @ 2023-11-30 1:30 ` Anton Yakovlev 2023-11-30 10:46 ` Matias Ezequiel Vara Larsen 0 siblings, 1 reply; 6+ messages in thread From: Anton Yakovlev @ 2023-11-30 1:30 UTC (permalink / raw) To: Matias Ezequiel Vara Larsen, virtio-comment Hi Matias, On 07.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: > Ping Anton. > > Thanks, Matias. > > On Thu, Oct 5, 2023 at 11:41 AM Matias Ezequiel Vara Larsen > <mvaralar@redhat.com> wrote: >> >> This commit aims at providing a better definition of latency_bytes. To >> do so, this commit defines latency_bytes as is defined in Crosvm. >> >> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> >> --- >> device-types/sound/description.tex | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex >> index 54c9c8e..1349765 100644 >> --- a/device-types/sound/description.tex >> +++ b/device-types/sound/description.tex >> @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device >> \begin{description} >> \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, >> and VIRTIO_SND_S_IO_ERR otherwise. >> -\item[\field{latency_bytes}] indicates the current device latency. >> +\item[\field{latency_bytes}] indicates the current device latency. For >> +playback, this is the amount of bytes that must be consumed before >> +the current request can be played. For capture, this is the latency in terms of >> +bytes that the capture buffer was recorded. >> \end{description} Yes, this field definitely needs some clarification. If you think about it, from the point of view of the application in the guest, the size of the current latency is the current contents of the buffer. I.e. exactly what you added to the description, but without taking into account the value of this field. In the current Linux driver implementation, this "latency_bytes" value is saved to the "delay" field, which is then passed to user space. And this "delay", as I understand it, indicates an additional delay caused by the specifics of the hardware. And it turns out that the latency_bytes field either should indicate such an additional delay (for example, caused by the specific implementation of the backend on the device side), or does not make sense, since the current latency value is already known a priori. What do you think? >> >> Since all buffers in the queue (with one exception) should be of the size >> -- >> 2.41.0 >> > -- Anton Yakovlev Senior Software Engineer OpenSynergy GmbH Rotherstr. 20, 10245 Berlin This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* [virtio-comment] Re: [PATCH] virtio-sound: add latency_bytes definition 2023-11-30 1:30 ` Anton Yakovlev @ 2023-11-30 10:46 ` Matias Ezequiel Vara Larsen 2023-12-08 2:45 ` Anton Yakovlev 0 siblings, 1 reply; 6+ messages in thread From: Matias Ezequiel Vara Larsen @ 2023-11-30 10:46 UTC (permalink / raw) To: Anton Yakovlev; +Cc: virtio-comment Hello Anton, On Thu, Nov 30, 2023 at 10:30:35AM +0900, Anton Yakovlev wrote: > Hi Matias, > > > On 07.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: > > Ping Anton. > > > > Thanks, Matias. > > > > On Thu, Oct 5, 2023 at 11:41 AM Matias Ezequiel Vara Larsen > > <mvaralar@redhat.com> wrote: > > > > > > This commit aims at providing a better definition of latency_bytes. To > > > do so, this commit defines latency_bytes as is defined in Crosvm. > > > > > > Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> > > > --- > > > device-types/sound/description.tex | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex > > > index 54c9c8e..1349765 100644 > > > --- a/device-types/sound/description.tex > > > +++ b/device-types/sound/description.tex > > > @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device > > > \begin{description} > > > \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, > > > and VIRTIO_SND_S_IO_ERR otherwise. > > > -\item[\field{latency_bytes}] indicates the current device latency. > > > +\item[\field{latency_bytes}] indicates the current device latency. For > > > +playback, this is the amount of bytes that must be consumed before > > > +the current request can be played. For capture, this is the latency in terms of > > > +bytes that the capture buffer was recorded. > > > \end{description} > > Yes, this field definitely needs some clarification. > > If you think about it, from the point of view of the application in the guest, > the size of the current latency is the current contents of the buffer. I.e. > exactly what you added to the description, but without taking into account the > value of this field. > > In the current Linux driver implementation, this "latency_bytes" value is > saved to the "delay" field, which is then passed to user space. And this > "delay", as I understand it, indicates an additional delay caused by the > specifics of the hardware. Yes, I understood the same. For me, it was not clear how "delay" would be used by user applications. In crosvm, for example, `latency_bytes` is set to 0, but I'm not sure what would happen if it was set to something else. When I played around with different values, I didn't notice any difference in behavior. > And it turns out that the latency_bytes field either should indicate such an > additional delay (for example, caused by the specific implementation of the > backend on the device side), or does not make sense, since the current latency > value is already known a priori. What do you think? Do you mean that we could get rid of this field and add it in the future in case we need it? Or, to add to the description the fact that latency_bytes is a specific implementation value that adds additional delay? Also I do not understand how the `latency_bytes` value and the completion notification may interact. For example, a device could send completion notification immediately after a request is received and just set the correct value to the `latency_bytes` field to indicate how many bytes would take to the current buffer to be consumed. I can't see any issue with using the `latency_byte` value in that way. Thanks, Matias. This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* [virtio-comment] Re: [PATCH] virtio-sound: add latency_bytes definition 2023-11-30 10:46 ` Matias Ezequiel Vara Larsen @ 2023-12-08 2:45 ` Anton Yakovlev 2023-12-11 10:39 ` Matias Ezequiel Vara Larsen 0 siblings, 1 reply; 6+ messages in thread From: Anton Yakovlev @ 2023-12-08 2:45 UTC (permalink / raw) To: Matias Ezequiel Vara Larsen; +Cc: virtio-comment Hi Matias, On 30.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: > Hello Anton, > > On Thu, Nov 30, 2023 at 10:30:35AM +0900, Anton Yakovlev wrote: >> Hi Matias, >> >> >> On 07.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: >>> Ping Anton. >>> >>> Thanks, Matias. >>> >>> On Thu, Oct 5, 2023 at 11:41 AM Matias Ezequiel Vara Larsen >>> <mvaralar@redhat.com> wrote: >>>> >>>> This commit aims at providing a better definition of latency_bytes. To >>>> do so, this commit defines latency_bytes as is defined in Crosvm. >>>> >>>> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> >>>> --- >>>> device-types/sound/description.tex | 5 ++++- >>>> 1 file changed, 4 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex >>>> index 54c9c8e..1349765 100644 >>>> --- a/device-types/sound/description.tex >>>> +++ b/device-types/sound/description.tex >>>> @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device >>>> \begin{description} >>>> \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, >>>> and VIRTIO_SND_S_IO_ERR otherwise. >>>> -\item[\field{latency_bytes}] indicates the current device latency. >>>> +\item[\field{latency_bytes}] indicates the current device latency. For >>>> +playback, this is the amount of bytes that must be consumed before >>>> +the current request can be played. For capture, this is the latency in terms of >>>> +bytes that the capture buffer was recorded. >>>> \end{description} >> >> Yes, this field definitely needs some clarification. >> >> If you think about it, from the point of view of the application in the guest, >> the size of the current latency is the current contents of the buffer. I.e. >> exactly what you added to the description, but without taking into account the >> value of this field. >> >> In the current Linux driver implementation, this "latency_bytes" value is >> saved to the "delay" field, which is then passed to user space. And this >> "delay", as I understand it, indicates an additional delay caused by the >> specifics of the hardware. > > Yes, I understood the same. For me, it was not clear how "delay" would > be used by user applications. In crosvm, for example, `latency_bytes` is > set to 0, but I'm not sure what would happen if it was set to something > else. When I played around with different values, I didn't notice any > difference in behavior. The value of this delay is reported to user space, and can also be taken into account when calculating timestamps for the substream. So the application can take this into account if necessary. >> And it turns out that the latency_bytes field either should indicate such an >> additional delay (for example, caused by the specific implementation of the >> backend on the device side), or does not make sense, since the current latency >> value is already known a priori. What do you think? > > Do you mean that we could get rid of this field and add it in the future > in case we need it? Or, to add to the description the fact that > latency_bytes is a specific implementation value that adds additional > delay? I meant that we could add something like: "indicates the current value of the additional delay caused by the implementation of the device". > Also I do not understand how the `latency_bytes` value and the > completion notification may interact. For example, a device could send > completion notification immediately after a request is received and just > set the correct value to the `latency_bytes` field to indicate how many > bytes would take to the current buffer to be consumed. I can't see any > issue with using the `latency_byte` value in that way. But what is the practical meaning of this? And, ideally, the completion of requests should coincide with period boundaries on the timeline. Otherwise, for example, there will be problems with synchronizing video and audio streams when timestamps based on the hw_ptr value are used. Best regards, > > Thanks, Matias. > -- Anton Yakovlev Senior Software Engineer OpenSynergy GmbH Rotherstr. 20, 10245 Berlin This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* [virtio-comment] Re: [PATCH] virtio-sound: add latency_bytes definition 2023-12-08 2:45 ` Anton Yakovlev @ 2023-12-11 10:39 ` Matias Ezequiel Vara Larsen 0 siblings, 0 replies; 6+ messages in thread From: Matias Ezequiel Vara Larsen @ 2023-12-11 10:39 UTC (permalink / raw) To: Anton Yakovlev; +Cc: virtio-comment Hello Anton, On Fri, Dec 08, 2023 at 11:45:18AM +0900, Anton Yakovlev wrote: > Hi Matias, > > On 30.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: > > Hello Anton, > > > > On Thu, Nov 30, 2023 at 10:30:35AM +0900, Anton Yakovlev wrote: > > > Hi Matias, > > > > > > > > > On 07.11.2023 19:46, Matias Ezequiel Vara Larsen wrote: > > > > Ping Anton. > > > > > > > > Thanks, Matias. > > > > > > > > On Thu, Oct 5, 2023 at 11:41 AM Matias Ezequiel Vara Larsen > > > > <mvaralar@redhat.com> wrote: > > > > > > > > > > This commit aims at providing a better definition of latency_bytes. To > > > > > do so, this commit defines latency_bytes as is defined in Crosvm. > > > > > > > > > > Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> > > > > > --- > > > > > device-types/sound/description.tex | 5 ++++- > > > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex > > > > > index 54c9c8e..1349765 100644 > > > > > --- a/device-types/sound/description.tex > > > > > +++ b/device-types/sound/description.tex > > > > > @@ -694,7 +694,10 @@ \subsubsection{PCM I/O Messages}\label{sec:Device Types / Sound Device / Device > > > > > \begin{description} > > > > > \item[\field{status}] contains VIRTIO_SND_S_OK if an operation is successful, > > > > > and VIRTIO_SND_S_IO_ERR otherwise. > > > > > -\item[\field{latency_bytes}] indicates the current device latency. > > > > > +\item[\field{latency_bytes}] indicates the current device latency. For > > > > > +playback, this is the amount of bytes that must be consumed before > > > > > +the current request can be played. For capture, this is the latency in terms of > > > > > +bytes that the capture buffer was recorded. > > > > > \end{description} > > > > > > Yes, this field definitely needs some clarification. > > > > > > If you think about it, from the point of view of the application in the guest, > > > the size of the current latency is the current contents of the buffer. I.e. > > > exactly what you added to the description, but without taking into account the > > > value of this field. > > > > > > In the current Linux driver implementation, this "latency_bytes" value is > > > saved to the "delay" field, which is then passed to user space. And this > > > "delay", as I understand it, indicates an additional delay caused by the > > > specifics of the hardware. > > > > Yes, I understood the same. For me, it was not clear how "delay" would > > be used by user applications. In crosvm, for example, `latency_bytes` is > > set to 0, but I'm not sure what would happen if it was set to something > > else. When I played around with different values, I didn't notice any > > difference in behavior. > > The value of this delay is reported to user space, and can also be taken into > account when calculating timestamps for the substream. So the application > can take this into account if necessary. > > Got it. Thanks for the explanation. > > > And it turns out that the latency_bytes field either should indicate such an > > > additional delay (for example, caused by the specific implementation of the > > > backend on the device side), or does not make sense, since the current latency > > > value is already known a priori. What do you think? > > > > Do you mean that we could get rid of this field and add it in the future > > in case we need it? Or, to add to the description the fact that > > latency_bytes is a specific implementation value that adds additional > > delay? > > I meant that we could add something like: "indicates the current value of the > additional delay caused by the implementation of the device". > Thanks, I will add that in the PATCH. > > > Also I do not understand how the `latency_bytes` value and the > > completion notification may interact. For example, a device could send > > completion notification immediately after a request is received and just > > set the correct value to the `latency_bytes` field to indicate how many > > bytes would take to the current buffer to be consumed. I can't see any > > issue with using the `latency_byte` value in that way. > > But what is the practical meaning of this? > > And, ideally, the completion of requests should coincide with period > boundaries on the timeline. Otherwise, for example, there will be problems > with synchronizing video and audio streams when timestamps based on the hw_ptr > value are used. > > Thanks for the clarification. Matias This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/ ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-12-11 10:39 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2023-10-05 9:41 [virtio-comment] [PATCH] virtio-sound: add latency_bytes definition Matias Ezequiel Vara Larsen 2023-11-07 10:46 ` [virtio-comment] " Matias Ezequiel Vara Larsen 2023-11-30 1:30 ` Anton Yakovlev 2023-11-30 10:46 ` Matias Ezequiel Vara Larsen 2023-12-08 2:45 ` Anton Yakovlev 2023-12-11 10:39 ` Matias Ezequiel Vara Larsen
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