Re: [PATCH 0/4] media: Track v4l2 buffers through an allocator
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From: Diederik de Haas <hidden>
Date: 2026-09-24 13:52:09
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Hi, On Thu Sep 24, 2026 at 2:36 PM CEST, Detlev Casanova wrote:
On Sunday, September 20, 2026 9:50:24 a.m. Eastern Daylight Time Diederik de Haas wrote:quoted
On Wed Sep 16, 2026 at 4:25 PM CEST, Detlev Casanova wrote:quoted
Currently, the only way to track buffers allocated by v4l2 from usespace is to use the subsystem available debug information (e.g.: /sys/kernel/debug/dma_buf/bufinfo). But that information is generic and cannot be matched to a v4l2 driver or to a userspace application: It is merely information about the allocation. ... Note that this depends on the ftrace support patch series[1] that provides fd/pid info in the v4l2_fh struct. That series is a bit old, so this is based on an older linux version, but that only changes things for the last 2 commits. A v4l2top utility[2] has been made, to be used in parallel with the fdinfo patch series[3], to show the list of active streams with their HW and memory usage. With this, debugfs looks like this when decoding a HEVC 1080p stream with rkvdec on rk3588: root # cat /sys/kernel/debug/v4l2/fdc38100.video-codec/mem created-by fd pid size label ----------------------------------------------------------------------- ...I build a kernel with your 3 patch series and I also build the v4l2top utility. Cool tool :-D Especially after I found out I should build the 'upstream' branch ;-) There were a couple of things I noticed: 1) With 'plain' kernel 7.3-rc3 but also with all my patches included, but excluding the patches from this series, I see this: ... Checking v4l2 debug dir again results in this:root@nanopc-t6-plus:~# ls -lh /sys/kernel/debug/v4l2/ total 0 drwxr-xr-x 2 root root 0 Sep 20 15:13 fdb60000.rga drwxr-xr-x 2 root root 0 Sep 20 15:13 fdb80000.rga drwxr-xr-x 2 root root 0 Sep 20 15:13 fdc38000.video-codec drwxr-xr-x 2 root root 0 Sep 20 15:13 fdee0000.hdmi_receiverI noticed my video-codec address was slightly different from yours.Yes, mine is on rk3588. A different SoC will have a different device register address.
That's why I noticed/mentioned it as mine is rk3588 too. Maybe this commit?
b481c11cd20a ("arm64: dts: rockchip: Update vdec register blocks order on RK3588")
quoted
Playing a 1080p BBB x264 video with a patched ffmpeg+mpv, results in this: ... And looking at the v4l2top utility, I noticed the following: 1. I see differing indications of the load while it's playing :-D\o/
Just did another quick test (for 3.) and noticed sometimes green 'lines' and sometimes red 'lines'. Any significance to the color? There also seems to be some kind of 'delay' when stopping a video and playing another one (can be the same video). It looks like it's 'flatlining' until the line of the previous video is scrolled off ... and then it seems to 'repaint' itself as the 'flatline' comes back alive :-P But this is REALLY minor and not bothersome at all.
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2. The ``Clock rate`` is always 750.0MHz (or 786431991Hz) (expected I think?)Yes, the clock won't change, for now at least. Some decoders could adapt their clocks depending on the work. The frequency value will also be used to determine exact core usage for those that expose a used cycle count after each job (I did not implement that yet in v4l2top)quoted
3. The ``Total Memory`` is always 0B and the ``Memory usage details`` column is always empty. That's also the case when I press one of the arrow keys which seems to select the entry. Am I missing sth or doing sth wrong?My guess would be that you didn't run it as root (this is usually needed to access the debugfs*). But if you did, we will have to dig a little.
I did indeed not run it as root the first time around. But just did another test and with root the memory data is displayed :-) Cheers, Diederik
*: Note that later, we'd like to report global memory usage through fdinfo, so that the metric is accessible as a user, with buffer details still from the debugfs (so that'd need root access) Detlev.quoted
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[1]: https://lore.kernel.org/all/20260610-v4l2-add-ftrace-v2-0-9756edf72ac1@co llabora.com/ [2]: https://github.com/cazou/v4l2top/tree/upstream [3]: https://lore.kernel.org/all/20260706-v4l2-add-fdinfo-v3-0-d556568cf38e@co llabora.com/ Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com> --- Detlev Casanova (4): media: Add a v4l2 memory allocations tracker media: Store v4l2_fh in the vb_queue media: verisilicon: Switch to tracked dma allocations media: rkvdec: Switch to tracked dma allocations drivers/media/common/videobuf2/Makefile | 1 + drivers/media/common/videobuf2/v4l2-allocator.c | 186 +++++++++++++++++++++ .../media/common/videobuf2/videobuf2-dma-contig.c | 27 ++- .../media/platform/rockchip/rkvdec/rkvdec-h264.c | 14 +- .../media/platform/rockchip/rkvdec/rkvdec-hevc.c | 14 +- .../media/platform/rockchip/rkvdec/rkvdec-rcb.c | 21 ++- .../platform/rockchip/rkvdec/rkvdec-vdpu381-h264.c | 14 +- .../platform/rockchip/rkvdec/rkvdec-vdpu381-hevc.c | 14 +- .../platform/rockchip/rkvdec/rkvdec-vdpu383-h264.c | 14 +- .../platform/rockchip/rkvdec/rkvdec-vdpu383-hevc.c | 14 +- .../media/platform/rockchip/rkvdec/rkvdec-vp9.c | 33 ++-- drivers/media/platform/rockchip/rkvdec/rkvdec.c | 4 + drivers/media/platform/verisilicon/hantro.h | 1 + drivers/media/platform/verisilicon/hantro_drv.c | 4 + drivers/media/platform/verisilicon/hantro_h264.c | 7 +- drivers/media/platform/verisilicon/hantro_hevc.c | 100 ++++++----- drivers/media/platform/verisilicon/hantro_mpeg2.c | 16 +- .../media/platform/verisilicon/hantro_postproc.c | 14 +- drivers/media/platform/verisilicon/hantro_vp8.c | 25 +-- drivers/media/platform/verisilicon/hantro_vp9.c | 34 +++- .../verisilicon/rockchip_vpu981_hw_av1_dec.c | 160 +++++++++++------- drivers/media/v4l2-core/v4l2-device.c | 4 +- include/media/v4l2-allocator.h | 26 +++ include/media/v4l2-device.h | 2 + include/media/videobuf2-core.h | 3 + 25 files changed, 555 insertions(+), 197 deletions(-) --- base-commit: 66affa37cfac0aec061cc4bcf4a065b0c52f7e19 change-id: 20260612-v4l2-add-mem-tracker-da0088c74a64 prerequisite-change-id: 20260608-v4l2-add-ftrace-aec6e7f60a6c:v2 prerequisite-patch-id: bd45b4df66799a7f9f22b49973a78d1bd3590a4a prerequisite-patch-id: 6a5ed5615f08257cf854d441785066b5ff4d5d47 prerequisite-patch-id: 02594c869498b9e91e416d70242afbaa6b3a8d6a prerequisite-patch-id: 9f25ec78f3b99ac1c5d42eb732f5bd9eae73fadd prerequisite-patch-id: 4ed2c2e8c3abfa7f6328d0ea4f488ca5a3eec8fb prerequisite-patch-id: 8787d50eb80e1a63a57a123268cade23c9e64618 prerequisite-patch-id: bfe85822378fa771f9bbc3e1e8c8ff6bce0eb7fd prerequisite-patch-id: 784d0801da320f7b41194f4632ee422c32f1b5b8 prerequisite-patch-id: 362c8366e2efbfb5e6f1a3f71cfddbd46e8d1506 Best regards, -- Detlev Casanova [off-list ref] _______________________________________________ Linux-rockchip mailing list Linux-rockchip@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-rockchip