[libcamera-devel] [PATCH 2/2] libcamera: pipeline-handler: Consider max in-flight requests constraint
Paul Elder
paul.elder at ideasonboard.com
Wed Dec 14 13:13:06 CET 2022
Hi,
On Wed, Dec 14, 2022 at 10:19:54AM +0100, Jacopo Mondi via libcamera-devel wrote:
> Hi Umang
>
> On Wed, Dec 14, 2022 at 02:11:12PM +0530, Umang Jain wrote:
> > Hi Jacopo
> >
> > On 12/14/22 1:29 PM, Jacopo Mondi wrote:
> > > Hi Umang
> > >
> > > On Wed, Dec 14, 2022 at 11:07:25AM +0530, Umang Jain wrote:
> > > > Hi Jacopo,
> > > >
> > > > On 12/13/22 9:25 PM, Jacopo Mondi wrote:
> > > > > Hi Umang,
> > > > >
> > > > > On Mon, Dec 12, 2022 at 08:32:56PM +0530, Umang Jain via libcamera-devel wrote:
> > > > > > This patch introduces a new constraint in the pipeline handler base
> > > > > > class which allows various derived pipeline handlers to set and
> > > > > > restrict the number of maximum in-flight requests that can be queued to
> > > > > > the underlying components (for e.g. the IPA).
> > > > > It's my understanding that the max number of in-flight requests is
> > > > > what the properties::PipelineDepth property expresses.
> > > > Indeed, that's why understanding as well. The properties::PipelineDepth
> > > > should be set by the pipeline-handlers.
(Besides the fact that I can't find properties::PipelineDepth)
controls::PipelineDepth says that it "Specifies the number of pipeline
stages the frame went through from when it was exposed to when the final
completed result was available to the framework.", which to me sounds
like the *minimum* amount of in-flight requests.
I thought that here we're defining the *maximum* allowed in-flight
requests. Not that all of the requests have to actually be doing
something in hardware, but that it's the amount of requests the the
pipeline handler is capable of handling internally without overflowing.
> > > >
> > > > We need to identify and atleast agree upon the correct PipelineDepth for the
> > > > two platforms that uses the FCQueue (IPU3 and RkISP1) as well. Some grey
> > > > areas there as well
> > > I think 16 is fine for now. At least doesn't change what we already
> > > have today
> > >
> > > > > Can't we access that property at queue request time, or maybe better we
> > > > > could cache it at camera registration time, since it's constant ?
> > > > If we intent to use the properties::PipelineDepth, as the size of the
> > > > FCQueue - it needs to exist / set before IPA is constructed.
> > > >
> > > > (See IPAIPU3::IPAIPU3() for context)
> > > >
> > > The property can still be defined in the IPA header as IPA can access
> > > it safely.
> >
> > You mean via a global const variable like it's done in Patch 1/2 ?
>
> Yes, like in patch 1/2
>
>
> > >
> > > Pipeline Handlers will have to register the property -before- the
> > > camera is registered, but looking at IPU3 that's already the case now
> > > (data->properties_ gets populated before calling registerCamera())
> > >
> > >
> > > > So I think queue request time is quite late there. Camera registeration time
> > > > might be possible with some changes (looking at
> > > > PipelineHandlerIPU3::registerCameras())
> > > What I meant is either
> > >
> > > 1) At PipelineHandler::queueRequest() time, the PipelineHandler base
> > > class accesses Camera::properties() and fetches
> > > properties::PipelineDepth
> >
> > I think it's a over-kill here. queueRequest() is a recurring call and I
> > don't want fetching of PipelineDepth here.
Oh one hand, yeah imo getting it from Camera::properties() is more
correct, but on the other hand it does indeed seem overkill.
>
> While I consider a lookup on an unordered_map<> of a few items not
> that expensive, I agree it's in an hot path, and it would be better to
> cache the value somewhere. Caching it inside Camera or Camera::Private
> is a duplication, as it's already part of
> Camera::Private::properties_, but I would be fine with the
> PipelineHandler base class doing something like this (as proposed in
> my previous 2) point below)
>
> void PipelineHandler::registerCamera(std::shared_ptr<Camera> camera)
> {
>
> /* Cache the pipeline depth in the Camera private data. */
> const auto &pipelineDepth = camera->properties().get(properties::PipelineDepth);
>
> Camera::Private *data = camera->_d();
> data->pipelineDepth = pipelineDepth ? 0 : *pipelineDepth;
>
> ...
> }
>
> Otherwise the PipelineHandler base class can be added with a class
> member, and each registred camera will overwrite that value, it's less
> nice, but all cameras from the same PH instance will have the same
> pipeline depth, so...
Perhaps caching would be a good middle ground.
>
>
> > > 2) At PipelineHandler::registerCamera() time the property value is
> > > cached, but this would require to cache per-camera data in
> > > PipelineHandler, something we don't have, or to populate a class
> > > member of Camera::Private for that purpose..
> >
> > That's interesting because I initially didn't think of multiple cameras
> > registered with one instance of pipeline-handler.
> > It also makes me wonder -
> >
> > - Is properties::PipelineDepth Camera specific or platform-specific ? Seems
> > now it's Camera specific
> > - Then defining it IPA headers won't be a good option, in cases where
> > PipelineDepth for different cameras differ.
>
> Why camera specific ? Each camera will indeed register it as a
> property for applications to retrieve it, but the
> value depends on the platform afaict and it can be a compile-time constant
> defined by the IPA headers. Even better, the same compile-time
> constant will be used to size the FCQ.
If it's platform-specific then wouldn't the pipeline handler have to
report it based on what platform it's running on? So we can't really
hardcode a constant. Maybe putting it in properties is indeed better.
>
> >
> > Need some thinking ...
> >
> > But none the less, this is a something that can be done on top with wider
> > discussion / context on PipelineDepth. It shouldn't necessarily block the
> > series.
>
> My whole point is that I think we should find a better mechanism for
> registering pipeline depth compared to having pipeline handlers call
> setMaxQueueRequests() as it requires an explicit action that can
> easily be overlooked, while we want the queue overflow protection to
I mean, we could initialize kMaxFrameContexts to an invalid value (-1?)
and then force *all* pipeline handlers to explictly set it, even if to
zero. Then it becomes really easy to catch.
Or note it down as a compliancy thing and have lc-compliance test for
it. I presume this will become a required property to be exposed anyway.
In any case, the goal is to report to the user the "maximum number of
requests that are allowed to be queued in the camera", right? So it'll
have to go through properties anyway. Perhaps then it's best to expose
it via properties (as it's already the interface we have for exposing
properties to the user), and then the base PipelineHandler can cache it
for the queuing guard. That would get rid of the special explicit call,
and would still achieve the goal.
I suppose then we'd actually need a compliance test for the property,
but I guess we have a few more of those anyway.
My two cents.
Paul
> happen transparently if a pipeline handler register
> properties::PipelineDepth ? Am I overthinking this ?
>
>
> > >
> > > Sorry for not having been clear
> > >
> > >
> > > >
> > > > > Also, can this feature be tested in test/ ? Probably not, as it
> > > > > requires a compliant pipeline handler ? Maybe vimc can be instrumented
> > > > I have been thinking about that as well. It's shouldn't be too difficult.
> > > > > ?
> > > > >
> > > > > > The pipeline handler is now equipped with the responsibility of not to
> > > > > > over queue the requests to the underlying layers. The derived
> > > > > > pipeline handler (or even IPA) can also have various kind of requests
> > > > > > queue(arrays, queues or ring-buffer) hence, it might be an issue where
> > > > > > the application queues the requests at a rate where these kind of
> > > > > > queues can over-flow. The patch ensures that the base PipelineHandler
> > > > > > will never let the requests overflow to underlying layers, once the
> > > > > > derived pipeline handler sets its maximum capacity of handling
> > > > > > in-flight requests using PipelineHandler::setMaxQueueRequests().
> > > > > >
> > > > > > The queue request management introduced in the pipeline handler base
> > > > > > class is now used by the IPU3 and RkISP1 pipeline handlers. This will
> > > > > > prevent over-writing of frame contexts (i.e. FCQueue) in these two
> > > > > > pipeline handlers.
> > > > > >
> > > > > > Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> > > > > > ---
> > > > > > include/libcamera/internal/pipeline_handler.h | 4 ++
> > > > > > src/libcamera/pipeline/ipu3/ipu3.cpp | 1 +
> > > > > > src/libcamera/pipeline/rkisp1/rkisp1.cpp | 1 +
> > > > > > src/libcamera/pipeline_handler.cpp | 51 ++++++++++++++++++-
> > > > > > 4 files changed, 56 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/include/libcamera/internal/pipeline_handler.h b/include/libcamera/internal/pipeline_handler.h
> > > > > > index ec4f662d..83f8bd9f 100644
> > > > > > --- a/include/libcamera/internal/pipeline_handler.h
> > > > > > +++ b/include/libcamera/internal/pipeline_handler.h
> > > > > > @@ -70,6 +70,7 @@ public:
> > > > > > protected:
> > > > > > void registerCamera(std::shared_ptr<Camera> camera);
> > > > > > void hotplugMediaDevice(MediaDevice *media);
> > > > > > + void setMaxQueueRequests(uint32_t maxRequests);
> > > > > >
> > > > > > virtual int queueRequestDevice(Camera *camera, Request *request) = 0;
> > > > > > virtual void stopDevice(Camera *camera) = 0;
> > > > > > @@ -97,6 +98,9 @@ private:
> > > > > > Mutex lock_;
> > > > > > unsigned int useCount_ LIBCAMERA_TSA_GUARDED_BY(lock_);
> > > > > >
> > > > > > + uint32_t maxQueueRequests_;
> > > > > > + uint32_t requestsQueueCounter_;
> > > > > > +
> > > > > > friend class PipelineHandlerFactoryBase;
> > > > > > };
> > > > > >
> > > > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > index e4d79ea4..d1d42f78 100644
> > > > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > @@ -422,6 +422,7 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > > PipelineHandlerIPU3::PipelineHandlerIPU3(CameraManager *manager)
> > > > > > : PipelineHandler(manager), cio2MediaDev_(nullptr), imguMediaDev_(nullptr)
> > > > > > {
> > > > > > + setMaxQueueRequests(ipa::ipu3::kMaxFrameContexts);
> > > > > > }
> > > > > >
> > > > > > std::unique_ptr<CameraConfiguration>
> > > > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > > > > > index eb9ad65c..a48adba9 100644
> > > > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > > > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> > > > > > @@ -599,6 +599,7 @@ CameraConfiguration::Status RkISP1CameraConfiguration::validate()
> > > > > > PipelineHandlerRkISP1::PipelineHandlerRkISP1(CameraManager *manager)
> > > > > > : PipelineHandler(manager), hasSelfPath_(true)
> > > > > > {
> > > > > > + setMaxQueueRequests(ipa::rkisp1::kMaxFrameContexts);
> > > > > > }
> > > > > >
> > > > > > std::unique_ptr<CameraConfiguration>
> > > > > > diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> > > > > > index cfade490..103f9db0 100644
> > > > > > --- a/src/libcamera/pipeline_handler.cpp
> > > > > > +++ b/src/libcamera/pipeline_handler.cpp
> > > > > > @@ -67,7 +67,8 @@ LOG_DEFINE_CATEGORY(Pipeline)
> > > > > > * through the PipelineHandlerFactoryBase::create() function.
> > > > > > */
> > > > > > PipelineHandler::PipelineHandler(CameraManager *manager)
> > > > > > - : manager_(manager), useCount_(0)
> > > > > > + : manager_(manager), useCount_(0), maxQueueRequests_(0),
> > > > > > + requestsQueueCounter_(0)
> > > > > > {
> > > > > > }
> > > > > >
> > > > > > @@ -428,6 +429,9 @@ void PipelineHandler::doQueueRequest(Request *request)
> > > > > > Camera::Private *data = camera->_d();
> > > > > > data->queuedRequests_.push_back(request);
> > > > > >
> > > > > > + if (maxQueueRequests_)
> > > > > > + requestsQueueCounter_++;
> > > > > > +
> > > > > > request->_d()->sequence_ = data->requestSequence_++;
> > > > > >
> > > > > > if (request->_d()->cancelled_) {
> > > > > > @@ -455,6 +459,10 @@ void PipelineHandler::doQueueRequests()
> > > > > > if (!request->_d()->prepared_)
> > > > > > break;
> > > > > >
> > > > > > + if (maxQueueRequests_ &&
> > > > > > + requestsQueueCounter_ >= maxQueueRequests_)
> > > > > > + break;
> > > > > > +
> > > > > > doQueueRequest(request);
> > > > > > waitingRequests_.pop();
> > > > > > }
> > > > > > @@ -531,6 +539,9 @@ void PipelineHandler::completeRequest(Request *request)
> > > > > > ASSERT(!req->hasPendingBuffers());
> > > > > > data->queuedRequests_.pop_front();
> > > > > > camera->requestComplete(req);
> > > > > > +
> > > > > > + if (maxQueueRequests_)
> > > > > > + requestsQueueCounter_--;
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > @@ -647,6 +658,44 @@ void PipelineHandler::disconnect()
> > > > > > * constant for the whole lifetime of the pipeline handler.
> > > > > > */
> > > > > >
> > > > > > +/**
> > > > > > + * \var PipelineHandler::maxQueueRequests_
> > > > > > + * \brief Maximum number of in-flight requests that can be queued
> > > > > > + *
> > > > > > + * A hardware can handle a certain number of maximum requests at a given
> > > > > > + * point. If such a constraint exists, set maxQueueRequests_ via
> > > > > > + * \a setMaxQueueRequests() in the derived pipeline handler.
> > > > > > + *
> > > > > > + * The derived pipeline handler can choose not to define such constraint as
> > > > > > + * well. In that case, the derived pipeline handler can avoid setting
> > > > > > + * \a setMaxQueueReqeuests(), hence \a maxQueueRequests_ and
> > > > > > + * \a requestsQueueCounter_ will be 0.
> > > > > > + */
> > > > > > +
> > > > > > +/**
> > > > > > + * \var PipelineHandler::requestsQueueCounter_
> > > > > > + * \brief Number of requests queued to the underlying hardware
> > > > > > + *
> > > > > > + * If \a setMaxQueueRequests() is set by the derived pipeline handler,
> > > > > > + * requestsQueueCounter_ reflects the number of requests queued
> > > > > > + * to the underlying hardware by the pipeline handler.
> > > > > > + */
> > > > > > +
> > > > > > +/**
> > > > > > + * \brief Sets the maximum number of requests that can be queued
> > > > > > + * \param[in] maxRequests Maximum number of in-flight requests
> > > > > > + *
> > > > > > + * A hardware can handle a certain number of requests at a given point.
> > > > > > + * This function sets the maximum number of in-flight requests that can
> > > > > > + * be queued to the hardware by the pipeline handler. Each derived pipeline
> > > > > > + * handler should set the maximum number of in-flight requests it can handle
> > > > > > + * at a given point using this function, if at all such a constraint exists.
> > > > > > + */
> > > > > > +void PipelineHandler::setMaxQueueRequests(uint32_t maxRequests)
> > > > > > +{
> > > > > > + maxQueueRequests_ = maxRequests;
> > > > > > +}
> > > > > > +
> > > > > > /**
> > > > > > * \fn PipelineHandler::name()
> > > > > > * \brief Retrieve the pipeline handler name
> > > > > > --
> > > > > > 2.38.1
> > > > > >
> >
More information about the libcamera-devel
mailing list