Minimizing voxl-camera-server CPU usage in SDK1.6

Rowan Dempster

@Alex-Kushleyev Hi Alex, just following up on any update regarding the shared ION buffers or other methods to work around the CPU hit taken by having many clients to misp based image pipes. Happy to try out any methods/suggestions with our specific clients!

Rowan

Alex Kushleyev

Hi @Rowan-Dempster ,

I started a new branch where I will be working on some performance optimizations in the camera server.

https://gitlab.com/voxl-public/voxl-sdk/services/voxl-camera-server/-/tree/perf-optimizations

In my initial testing, setting cpu to perf and when running one or two instances of the following:

voxl-inspect-cam tracking_front_misp_norm tracking_down_misp_norm

i was seeing:

1 instance (2 inspected streams) : 42% CPU (of one core)
2 instances (4 inspected streams): 58% CPU (of one core)

with the changes i just committed, i am seeing:

1 instance: 31% cpu
2 instances : 36% cpu

If you would like you can test camera server from this branch and see if you can reproduce the results.

notes:

the internal buffers were switched from uncached to cached and proper buffer management was added to ensure that data written by GPU is properly accessed by CPU
with these changes, if you use the _encoded stream from the tracking camera, it will work, but in dmesg you will see messages related to qbuf cache ops failed -- this is still under investigation and will be fixed soon.

Meanwhile, I will work on an a simple example that shows the usage of ION buffers, I will try to share it a bit later today.

Alex

Alex Kushleyev

Hi @Rowan-Dempster ,

Please take a look at this example (you can build and run it too) : https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-mpa-tools/-/blob/add-new-image-tools/tools/voxl-image-repub.cpp

This app can accept a regular image (RAW8 or YUV) and either re-publish it unchanged or crop and publish the result. Sometimes this is useful for quickly cropping an image that is fed into a different application that expects a smaller image or different aspect ratio.

The app shows how to subscribe and handle ion buffer streams.

Usage:

voxl2:/$ voxl-image-repub                          
ERROR: Pipe name not specified

    
    Re-publish cropped camera frames (RAW8 or YUV)
    
    Options are:
    -x, --crop-offset-x    crop offset in horizontal dimension
    -y, --crop-offset-y    crop offset in vertical dimension
    -w, --crop-size-x      crop size in horizontal dimension (width)
    -h, --crop-size-y      crop size in vertical dimension (height)
    -o, --output-name      output pipe name
    -u, --usage            print this help message
    
    The cropped image will be centered if the crop offsets are not provided. 
    
    typical usage:
    /# voxl-image-repub tracking --crop-size-x 256 --crop-size-y 256
    /# voxl-image-repub tracking --crop-size-x 256 --crop-size-y 256 --crop-offset-x 128 --crop-offset-y 128

example re-publishing ion buffer image as regular image (which you can view in voxl-portal ) :

voxl-image-repub tracking_front_misp_norm_ion -o test

(you can see which ion pipes are available by running voxl-list-pipes | grep _ion)

Please note that without the previous fix that i posted above, the client process that receives and uncached ION buffer will incur extra CPU load while accessing this buffer. For example, the same voxl-image-repub client uses 1.7% cpu while republishing the normalized image (cached ion buffer), while using 7.3% cpu republishing an image from an uncached ION buffer. (cpu usage % using one of the smaller cores).

Please try and let me know if you have any questions.

I know this cached / uncached buffering may be a bit confusing, but i will document this a bit more to help explain it a little better.

Alex

Rowan Dempster

@Alex-Kushleyev Hi Alex, just acknowledging your messages, thanks for looking into this and providing us with a path forward. I will have time over the next 2-3 days to test the perf-optimizations branch and familiarize myself the ION based clients. I will update you then.

Alex Kushleyev

@Rowan-Dempster , sounds good, let me know how the testing goes.

Alex

Rowan Dempster

@Alex-Kushleyev Actually had some time today to do the profiling and explore the ION pipes.

I see the same improvements that you quoted:

On 2.2.17
Normal pipes: 45%
MISP pipes: 66%
MISP pipes + 4x tracking pipes: 160%

On perf improvements
Normal pipes: 45%
MISP pipes: 52%
MISP pipes + 4x tracking pipes: 71%

On perf improvements + ION pipes
MISP pipes: 48%
MISP pipes + 4x tracking pipes: 52%

I started looking into using the ION pipe in the QVIO server code but saw this in the voxl-mpa-tools build script:

	qrb5165)
		check_docker "4.3"
		mkdir -p build32
		cd build32
		cmake -DCMAKE_TOOLCHAIN_FILE=${TOOLCHAIN_QRB5165_1_32} \
				-DBUILD_TOOLS=OFF \
				-DEN_ION_BUF=OFF ../
		make -j$(nproc)
		cd ../
		mkdir -p build64
		cd build64
		cmake -DCMAKE_TOOLCHAIN_FILE=${TOOLCHAIN_QRB5165_1_64} \
				-DBUILD_TOOLS=ON \
				-DEN_ION_BUF=ON ../
		make -j$(nproc)
		cd ../
		;;

	qrb5165-2)
		check_docker "4.3"
		mkdir -p build
		cd build
		cmake -DCMAKE_TOOLCHAIN_FILE=${TOOLCHAIN_QRB5165_2_64} \
				-DBUILD_TOOLS=ON \
				-DEN_ION_BUF=OFF ../
		make -j$(nproc)
		cd ../
		;;

Since we're using the qrb5165 (not the qrb5165-2) we have to use the 32bit toolchain to build QVIO (right?):

	qrb5165)
		check_docker "4.4"
		mkdir -p build
		cd build
		cmake -DCMAKE_TOOLCHAIN_FILE=${TOOLCHAIN_QRB5165_1_32} ../
		make -j$(nproc)
		cd ../
		;;

Does this mean that on the qrb5165 (using the 32 bit toolchain), the QVIO server cannot be a client to the ION pipes?

Thank you,
Rowan

Alex Kushleyev

@Rowan-Dempster ,

Yes, QVIO only runs as a 32-bit app due to the nature of the library from Qualcomm.

I tried to build the voxl-image-repub application for 32 bit and got the following error:

/usr/bin/arm-linux-gnueabi-ld: CMakeFiles/voxl-image-repub.dir/voxl-image-repub.cpp.o: in function `main':
voxl-image-repub.cpp:(.text.startup+0x228): undefined reference to `pipe_client_set_ion_buf_helper_cb'

So it seems like the 32-bit version of libmodal-pipe does not support sending ION buffers.

I just checked with the team - even though we have not tested the ION buffer sharing in 32-bit environment, it should work. You could try to build libmodal-pipe library and enable ION support : https://gitlab.com/voxl-public/voxl-sdk/core-libs/libmodal-pipe/-/blob/master/build.sh?ref_type=heads#L76 .

Then you would need to install that new library into your docker container where you are building your app, as well as deploy to VOXL2.

BTW in order to build the tools in voxl-mpa-tools i needed to disable -Werror and comment out a few targets like voxl-convert-image and voxl-inspect-cam-ascii due to lack of 32-bit version of opencv.

So.. if you really wanted the QVIO app to use the shared ION buffers, you would have to go that route..

Alex

Rowan Dempster

@Alex-Kushleyev Hi Alex I'm running into compilation errors when building libmodal-pipe after turning the EN_ION_BUF flag ON (builds fine with the flag OFF)

Found voxl-cross version: 4.4
-- ---------------------------------------------------------
-- Using voxl-cross 32-bit toolchain for QRB5165
-- C Compiler     : /usr/bin/arm-linux-gnueabi-gcc-7
-- C++ Compiler   : /usr/bin/arm-linux-gnueabi-g++-7
-- Sysroot        : /opt/sysroots/qrb5165_1
-- C flags        : -isystem=/usr/arm-linux-gnueabi/include -isystem=/usr/include -idirafter /usr/include -fno-stack-protector -march=armv7-a -mfloat-abi=softfp -mfpu=vfpv4
-- CXX flags      : -isystem=/usr/arm-linux-gnueabi/include -isystem=/usr/include -idirafter /usr/include -fno-stack-protector -march=armv7-a -mfloat-abi=softfp -mfpu=vfpv4
-- EXE Link Flags : -L/opt/sysroots/qrb5165_1/usr/lib32 -L/opt/sysroots/qrb5165_1/lib -L/opt/sysroots/qrb5165_1/usr/lib -L/opt/sysroots/qrb5165_1/usr/arm-linux-gnueabi -L/opt/sysroots/qrb5165_1/usr/lib/gcc-cross/arm-linux-gnueabi/7 -L/usr/lib
-- SO Link Flags  : -L/opt/sysroots/qrb5165_1/usr/lib32 -L/opt/sysroots/qrb5165_1/lib -L/opt/sysroots/qrb5165_1/usr/lib -L/opt/sysroots/qrb5165_1/usr/arm-linux-gnueabi -L/opt/sysroots/qrb5165_1/usr/lib/gcc-cross/arm-linux-gnueabi/7 /opt/sysroots/qrb5165_1/usr/lib/gcc-cross/arm-linux-gnueabi/7/libgcc.a /opt/sysroots/qrb5165_1/usr/lib/gcc-cross/arm-linux-gnueabi/7/libgcc_eh.a /opt/sysroots/qrb5165_1/usr/lib/gcc-cross/arm-linux-gnueabi/7/libssp_nonshared.a /opt/sysroots/qrb5165_1/usr/arm-linux-gnueabi/lib/libc_nonshared.a -L/usr/lib
-- The C compiler identification is GNU 7.3.0
-- The CXX compiler identification is GNU 7.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/arm-linux-gnueabi-gcc-7 - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/arm-linux-gnueabi-g++-7 - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- INFO: building with ion buf support
-- INFO: building with mavlink support
INFO: Skipping Building Python Bindings
-- INFO: Skipping examples and tools
-- Configuring done (1.8s)
-- Generating done (0.0s)
-- Build files have been written to: /home/root/build32
[ 10%] Building C object library/CMakeFiles/modal_pipe.dir/src/start_stop.c.o
[ 30%] Building C object library/CMakeFiles/modal_pipe.dir/src/client.c.o
[ 30%] Building CXX object library/CMakeFiles/modal_pipe.dir/src/buffers.cpp.o
[ 50%] Building C object library/CMakeFiles/modal_pipe.dir/src/interfaces.c.o
[ 50%] Building C object library/CMakeFiles/modal_pipe.dir/src/sink.c.o
[ 60%] Building C object library/CMakeFiles/modal_pipe.dir/src/common.c.o
[ 70%] Building C object library/CMakeFiles/modal_pipe.dir/src/misc.c.o
[ 80%] Building C object library/CMakeFiles/modal_pipe.dir/src/server.c.o
[ 90%] Building CXX object library/CMakeFiles/modal_pipe.dir/src/buffers/gbm.cpp.o
/home/root/library/src/server.c: In function 'pipe_server_write_ion_buffer':
/home/root/library/src/server.c:1757:102: error: format '%ld' expects argument of type 'long int', but argument 5 has type 'int64_t {aka long long int}' [-Werror=format=]
         printf("server preparing to send ion buffer id %d (fd %d) to clients, n_clients: %d, time: %ld\n",
                                                                                                    ~~^
                                                                                                    %lld
                ion_buf->buffer_id, fd, c[ch].n_clients, _time_monotonic_ns());
                                                         ~~~~~~~~~~~~~~~~~~~~                          
/home/root/library/src/client.c: In function '_stop_helper_and_remove_pipe':
/home/root/library/src/client.c:1353:56: error: format '%ld' expects argument of type 'long int', but argument 3 has type 'int64_t {aka long long int}' [-Werror=format=]
         if(en_debug) printf("ch: %d, shutdown socket %ld ns\n", ch, _time_monotonic_ns());
                                                      ~~^            ~~~~~~~~~~~~~~~~~~~~
                                                      %lld
/home/root/library/src/client.c: In function 'pipe_client_close':
/home/root/library/src/client.c:1475:43: error: format '%ld' expects argument of type 'long int', but argument 3 has type 'int64_t {aka long long int}' [-Werror=format=]
         printf("ch: %d, shutdown socket %ld ms\n", ch, _time_monotonic_ns());
                                         ~~^            ~~~~~~~~~~~~~~~~~~~~
                                         %lld
cc1: all warnings being treated as errors
make[2]: *** [library/CMakeFiles/modal_pipe.dir/build.make:93: library/CMakeFiles/modal_pipe.dir/src/client.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
cc1: all warnings being treated as errors
make[2]: *** [library/CMakeFiles/modal_pipe.dir/build.make:149: library/CMakeFiles/modal_pipe.dir/src/server.c.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:106: library/CMakeFiles/modal_pipe.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

Seems like I'm going down an uncharted path here. I'm okay with spending my time charting it out since getting QVIO to work with ION pipes will save us critical CPU util. Does ModalAI have plans to switch the official SDK QVIO server release (for qrb5165) to using ION pipes (I saw ModalAI switched to using the MISP pipes for QVIO a few months ago, taking a CPU hit)?

Alex Kushleyev

@Rowan-Dempster, the errors above seem like print formatting issues, but i understand that there could be some others. If you want to try to resolve those and see if there are any more significant errors, I can help.

We do not plan to update QVIO to use ion pipes, mainly because QVIO only supports a single camera input, so the savings from going to ION buffers for a single camera is going to be very small. The majority of savings came from the buffer caching policy, which I pointed out in the previous email. Another reason is that we are now focusing on Open Vins, which does support multiple cameras.

We do plan to fix the buffer caching policy so to remove this extra cpu usage for the appropriate MISP outputs. The work is ongoing in the branch i mentioned above.

Are you running multiple instances of QVIO, one for each camera?

Alex

Rowan Dempster

@Alex-Kushleyev Sounds good, I proceeded with resolving the basic typing issues related to 32 bit monotonic time. Next issue is a linker error that looks a bit more tricky:

-- Build files have been written to: /home/root/build32
[ 10%] Building CXX object library/CMakeFiles/modal_pipe.dir/src/buffers.cpp.o
[ 40%] Building C object library/CMakeFiles/modal_pipe.dir/src/server.c.o
[ 40%] Building C object library/CMakeFiles/modal_pipe.dir/src/common.c.o
[ 40%] Building C object library/CMakeFiles/modal_pipe.dir/src/misc.c.o
[ 50%] Building CXX object library/CMakeFiles/modal_pipe.dir/src/buffers/gbm.cpp.o
[ 60%] Building C object library/CMakeFiles/modal_pipe.dir/src/interfaces.c.o
[ 70%] Building C object library/CMakeFiles/modal_pipe.dir/src/client.c.o
[ 80%] Building C object library/CMakeFiles/modal_pipe.dir/src/sink.c.o
[ 90%] Building C object library/CMakeFiles/modal_pipe.dir/src/start_stop.c.o
[100%] Linking CXX shared library libmodal_pipe.so
/opt/sysroots/qrb5165_1/usr/lib/libgbm.so: file not recognized: file format not recognized
collect2: error: ld returned 1 exit status
make[2]: *** [library/CMakeFiles/modal_pipe.dir/build.make:228: library/libmodal_pipe.so] Error 1
make[1]: *** [CMakeFiles/Makefile2:106: library/CMakeFiles/modal_pipe.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

Alex Kushleyev

@Rowan-Dempster , yeah that is going to be a problem.. I don't think we have a 32 bit version of libgbm.so for VOXL2. This library is used for allocating the ION buffers.

The next thing to try would be to remove the buffer allocation part from the 32-bit build. Actually receiving and reading the buffer does not involve libgbm. the client just gets a FD, which needs to be mmap'ed and used. (this would remove ability to allocate new ION buffers, which you actually don't need on the client side).

I just commented out the following from the library CMakeLists:

#list(APPEND LIBS_TO_LINK gbm)
#list(APPEND all_src_files src/buffers/gbm.cpp)

and here are the errors:

/usr/bin/aarch64-linux-gnu-ld: CMakeFiles/modal_pipe.dir/src/buffers.cpp.o: in function `mpa_ion_buf_pool_alloc_bufs':
buffers.cpp:(.text+0x10c): undefined reference to `allocate_one_buffer(mpa_ion_buf_t*, int, int, unsigned int, unsigned int)'
/usr/bin/aarch64-linux-gnu-ld: buffers.cpp:(.text+0x184): undefined reference to `init_buffer_allocator()'
/usr/bin/aarch64-linux-gnu-ld: CMakeFiles/modal_pipe.dir/src/buffers.cpp.o: in function `mpa_ion_buf_pool_delete_bufs':
buffers.cpp:(.text+0x24c): undefined reference to `delete_one_buffer(mpa_ion_buf_t*)'
/usr/bin/aarch64-linux-gnu-ld: buffers.cpp:(.text+0x2a0): undefined reference to `shutdown_buffer_allocator()'

You could try replacing those functions with a fatal print statement "not implemented". Maybe that would work?

Alex

Rowan Dempster

@Alex-Kushleyev Hi Alex, I compiled libmodal-pipe with ION client-only support in 32 bit builds. I then changed the voxl-mpa-tools toolchain to 32 bit and set the 32 bit toolchain to actually build the tool executables and removed the ones that didn't compile. After deploying those two modified packages to the VOXL2 and running the same repub command that I ran before, I am getting a runtime error while parsing the incoming ION buffers on the client side

voxl2:/$ voxl-image-repub top_misp_norm_ion -o top_misp_norm_ion_test                                                                                                                                                 
Subscribed to ION input pipe: top_misp_norm_ion                                                                                                                                                                       
invalid metadata, magic number=85, expected 1229934146                                                                                                                                                                
invalid metadata, magic number=85, expected 1229934146                                                                                                                                                                
invalid metadata, magic number=85, expected 1229934146

Tracking it down, it looks like the call to pipe_client_bytes_in_pipe in the _ion_buf_cb is what's printing the error. If I remove that line (so not returning if pipe_client_bytes_in_pipe returns 0) it prints some garbage (incorrect) metadata and then segfaults:

voxl2:/$ voxl-image-repub top_misp_norm_ion -o top_misp_norm_ion_test
Subscribed to ION input pipe: top_misp_norm_ion
CH0 Got input ion frame size: 10330x-2843, format: STEREO_NV12, stride: 50834, size: 396 bytes

Segmentation fault:
Fault thread: voxl-image-repu(tid: 7900)
Fault address: 0x4
Address not mapped.
Segmentation fault

Note that I didn't recompile voxl-camera-server on-top of the modified libmodal-pipe, don't think that would change anything.

Let me know if you want me to send you my diffs of libmodal-pipe (w.r.t. master) and voxl-mpa-tools (w.r.t. add-new-image-tools).

P.S. I also tried voxl-inspect-ion-stream top_misp_norm_ion (that tool is also 32 bit now) and it's printing garbage too

|         Pipe Name |  fd  |  bytes  | wide |  hgt |exp(ms)| gain | frame id |latency(ms)|  fps |  mbps  |t
| top_misp_norm_ion |    6 |     455 | 3237 |-29847 | 52.43 |-24576 |1448040524 |1955547.7  | 30.0 |    0.6

Alex Kushleyev

@Rowan-Dempster ,

I think you are close.. sure, if you want to share the diff or make a fork of the repos, I will try it out.

Alex

Rowan Dempster

@Alex-Kushleyev Here are the diffs:

libmodal-pipe: https://gitlab.com/rowan.dempster/libmodal-pipe/-/merge_requests/1/diffs
voxl-mpa-tools: https://gitlab.com/rowan.dempster/voxl-mpa-tools/-/merge_requests/1/diffs

Thanks for your help!