On 5/6/07, Laurent Pinchart <[EMAIL PROTECTED]> wrote:
On Sunday 06 May 2007, Markus Rechberger wrote:
> On 5/6/07, Laurent Pinchart <[EMAIL PROTECTED]> wrote:
> > Let's move this discussion to the linux-uvc-devel list. I CCed
> > video4linux-list for reference, please reply to linux-uvc-devel only to
> > avoid
> > flooding the video4linux list.
> >
> > On Saturday 05 May 2007, Markus Rechberger wrote:
> >
> > [snip non-uvc issues]
> >
> > > I'll just write all my considerations here, you can put the ML into CC
> > > and/or split up the topics:
> > >
> > > 1.)
> > > May 5 20:14:19 debian kernel: ekiga: page allocation failure.
> > > order:10, mode:0x0
> > > May 5 20:14:19 debian kernel: [__alloc_pages+629/646]
> > > __alloc_pages+0x275/0x286
> > > May 5 20:14:19 debian kernel: [__get_free_pages+26/51]
> > > __get_free_pages+0x1a/0x33
> > > May 5 20:14:19 debian kernel: [dma_alloc_coherent+170/222]
> > > dma_alloc_coherent+0xaa/0xde
> > > May 5 20:14:19 debian kernel: [pg0+513461816/1069679616]
> > > uvc_init_video_bulk+0xb7/0x143 [uvcvideo]
> > > May 5 20:14:19 debian kernel: [pg0+513462425/1069679616]
> > > uvc_video_enable+0xfe/0x121 [uvcvideo]
> > > May 5 20:14:19 debian kernel: [pg0+513458219/1069679616]
> > > uvc_v4l2_do_ioctl+0x830/0x8bf [uvcvideo]
> > > May 5 20:14:19 debian kernel: [dput+24/373] dput+0x18/0x175
> > > May 5 20:14:19 debian kernel: [__link_path_walk+2824/3148]
> > > __link_path_walk+0xb08/0xc4c
> > > May 5 20:14:19 debian kernel: [n_tty_receive_buf+3303/3378]
> > > n_tty_receive_buf+0xce7/0xd32
> > > May 5 20:14:19 debian kernel: [get_page_from_freelist+635/798]
> > > get_page_from_freelist+0x27b/0x31e
> > > May 5 20:14:19 debian kernel: [wakeup_kswapd+45/104]
> > > wakeup_kswapd+0x2d/0x68 May 5 20:14:19 debian kernel:
> > > [pg0+511673193/1069679616]
> > > video_usercopy+0x112/0x1a3 [videodev]
> > > May 5 20:14:19 debian kernel: [vma_prio_tree_insert+23/42]
> > > vma_prio_tree_insert+0x17/0x2a
> > > May 5 20:14:19 debian kernel: [vma_link+218/247] vma_link+0xda/0xf7
> > > May 5 20:14:19 debian kernel: [pg0+513458420/1069679616]
> > > uvc_v4l2_ioctl+0x3a/0x40 [uvcvideo]
> > > May 5 20:14:19 debian kernel: [pg0+513456123/1069679616]
> > > uvc_v4l2_do_ioctl+0x0/0x8bf [uvcvideo]
> > > May 5 20:14:19 debian kernel: [do_ioctl+76/98] do_ioctl+0x4c/0x62
> > > May 5 20:14:19 debian kernel: [vfs_ioctl+583/602]
> > > vfs_ioctl+0x247/0x25a May 5 20:14:19 debian kernel:
[sys_ioctl+51/76]
> > > sys_ioctl+0x33/0x4c May 5 20:14:19 debian kernel:
[syscall_call+7/11]
> > > syscall_call+0x7/0xb May 5 20:14:19 debian kernel:
> > > =======================
> > > May 5 20:14:19 debian kernel: Mem-info:
> > > May 5 20:14:19 debian kernel: DMA per-cpu:
> > > May 5 20:14:19 debian kernel: CPU 0: Hot: hi: 0, btch: 1 usd:
> > > 0 Cold: hi: 0, btch: 1 usd: 0
> > > May 5 20:14:19 debian kernel: Normal per-cpu:
> > > May 5 20:14:19 debian kernel: CPU 0: Hot: hi: 186, btch: 31 usd:
> > > 13 Cold: hi: 62, btch: 15 usd: 51
> > > May 5 20:14:19 debian kernel: Active:93485 inactive:7268 dirty:0
> > > writeback:0 unstable:0 free:1171 slab:5255 mapped:15182 pagetables:980
> > > May 5 20:14:19 debian kernel: DMA free:1928kB min:92kB low:112kB
> > > high:136kB active:10716kB inactive:0kB present:16256kB
> > > pages_scanned:429 all_unreclaimable? no
> > > May 5 20:14:19 debian kernel: lowmem_reserve[]: 0 459
> > > May 5 20:14:19 debian kernel: Normal free:2756kB min:2692kB
> > > low:3364kB high:4036kB active:363224kB inactive:29072kB
> > > present:470284kB pages_scanned:291 all_unreclaimable? no
> > > May 5 20:14:19 debian kernel: lowmem_reserve[]: 0 0
> > > May 5 20:14:19 debian kernel: DMA: 4*4kB 1*8kB 1*16kB 1*32kB 1*64kB
> > > 0*128kB 1*256kB 1*512kB 1*1024kB 0*2048kB 0*4096kB = 1928kB
> > > May 5 20:14:19 debian kernel: Normal: 47*4kB 5*8kB 12*16kB 3*32kB
> > > 1*64kB 1*128kB 0*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 2756kB
> > > May 5 20:14:19 debian kernel: Swap cache: add 440134, delete 421407,
> > > find 136779/175577, race 0+0
> > > May 5 20:14:19 debian kernel: Free swap = 455676kB
> > > May 5 20:14:19 debian kernel: Total swap = 976888kB
> > > May 5 20:14:19 debian kernel: Free swap: 455676kB
> > > May 5 20:14:19 debian kernel: 122592 pages of RAM
> > > May 5 20:14:19 debian kernel: 0 pages of HIGHMEM
> > > May 5 20:14:19 debian kernel: 1844 reserved pages
> > > May 5 20:14:19 debian kernel: 70305 pages shared
> > > May 5 20:14:19 debian kernel: 18727 pages swap cached
> > > May 5 20:14:19 debian kernel: 0 pages dirty
> > > May 5 20:14:19 debian kernel: 0 pages writeback
> > > May 5 20:14:19 debian kernel: 15182 pages mapped
> > > May 5 20:14:19 debian kernel: 5253 pages slab
> > > May 5 20:14:19 debian kernel: 980 pages pagetables
> > >
> > > This happens either if a box has 256 mb ram, or is almost out of
> > > physical memory.
> > > The other driver I have works properly with it. After a fresh reboot
> > > the uvcvideo driver seems to work for a while.
> >
> > Oh, an OOM issue.
> >
> > The driver allocates memory for bulk/isochronous transfers based on two
> > parameters. The first one is the maximum payload transfer size, as
> > reported by the device. I can't do much about that one. The second one
is
> > the number of URBs allocated by the driver. This is currently hardcoded
> > to 5, but could be made configurable or could be computed based on the
> > maximum payload transfer size. I'll look into this issue.
>
> this really seems to be an issue with usb_buffer_alloc() after that
> call fails the whole memory management goes dizzy.
> It tries to swap out almost all the physical memory hangs for a while
> and copies the swapped memory back to physical memory till it becomes
> normal again.
> I also see that more than half of the system memory is used as cache,
> since usb_buffer_alloc is called with GFP_KERNEL it might wait until
> some cache memory gets released for it. I added Greg to that mail
> since I think that he knows alot about the usb framework itself.
If the system goes unstable when I try to request more than the available
memory, there's not much I can do about it. The driver fails gracefully when
memory allocation fails. I seriously doubt that the kernel memory manager
makes the system unstable when a driver tries to allocate a usb buffer
bigger
than the available memory. Maybe you have an issue specific to your system ?
I'm not familiar with the memory allocator internals, maybe Greg will be
able
to help.
It is like I explained it above. The system becomes very slow because
of moving almost everything to swap and copying it back to memory
again.
> dwMaxVideoFrameBufferSize 2752512 (which is used for
> usb_buffer_alloc, seems to be too much already)
The bulk buffers are allocated using dwMaxPayloadTransferSize. Isochronous
buffers are allocated using dwMaxVideoFrameSize, which is clearly a bug. I'm
working on a fix.
The stack trace you posted shows your device uses bulk transfers. Could you
tell me how big dwMaxPayloadTransferSize is ? If the devices insists on
using
huge buffers, there's not much I can do about it.
I simply wouldn't allocate that much memory for the urbs, this way
seems to work reliable with the driver I have.
I added some debug at the allocation it is 2.7 MB/URB
> I don't have a problem with that in my uvc driver since I only
> allocate memory for max. 640x480 and do not support a higher mode.
The comparison is thus not fair, is it ?
I explained it the wrong way, my driver allocates much less than your
one for the URBs and it also works reliable when all the system memory
is in use (system + cache)
> > Could you please post the output of lsusb -v (with usbutils 0.72 or
> > later) ? Thanks.
>
> (think that value was what you were looking for)
I'm interested in the lsusb output as well (the dwMaxPayloadTransferSize
value
is also interesting and not reported by the usb descriptors).
attached the uvc log.
> > > 2.) No v4l1 support using the compat layer
> > >
> > > I read some discussions about not supporting v4l1, as a point from the
> > > userside it simply has to work and there are still applications out
> > > there which only support v4l1, I read that a compat version of that
> > > driver is available but you don't want it in the main driver.
> >
> > The Linux UVC driver calls v4l_compat_translate_ioctl() for all
> > non-handled ioctls. The compat layer is thus used. It seems the problem
> > comes from a required v4l1 ioctl not handled properly by the compat
> > layer. I haven't looked into that issue, as I don't plan to support v4l1
> > explicitly in the driver.
>
> as for my drivers I always saw this as an open issue too, there is no
> reason to not add support for it at least, it just requires a few more
> ioctl controls.
Applications should be ported to v4l2. It's difficult to push application
developers to port their software if everything is still completely v4l1
compatible.
should yes but it's not so much work to add v4l1 compatibilty support
> > > 3.) Some controls are missing, for example mplayer isn't supported by
> > > just running
> > > mplayer -tv driver=v4l2 tv://
> >
> > mplayer is buggy. It doesn't set the v4l2_buffer.memory field prior to
> > dequeuing buffers, as required by the v4l2 specification. I think a
patch
> > has
> > been applied to the mplayer repository to fix this issue.
>
> I see xawtv doesn't work either here, the em28xx driver works with
> both without the need of any patches. xawtv is used as a reference for
> some other userspace applications since it has been available for a
> very long time already.
xawtv is buggy too, unfortunately. Many drivers don't check the
v4l2_buffer.memory field when handling VIDIOC_DQBUF, which leads to buggy
applications being undetected. We should either fix all drivers to check the
memory field, or change the v4l2 spec to remove the requirement.
The v4l2 specs are drafted, in that case it's better to fix the
uvcvideo driver and correct the specs if you want to get it work.
If you see a serious problem in that i'd be curious to know about it,
I haven't experienced any problems with the em28xx nor other drivers.
> > > 4.) read() isn't supported
> >
> > That's right, and this is definitely a shortcomming. I plan to support
> > read(),
> > but this hasn't been done yet. If you need read() support for a specific
> > application, we could work together to add it to the driver as quickly
as
> > possible.
> >
> > > 5.) I'd like to share common code between usb video devices, the
> > > em28xx driver supports slicing the video and piping a part of the
> > > video to /dev/vbi for example (raw vbi).
> > > 6.) Mauro also wrote some ideas about having a general usb framework
> > > since all devices share common parts.
> > >
> > > these points would be part of the agenda which I'd like to discuss
> > > with you and Mauro actually.
> >
> > I plan to see if I can use video-buf in the Linux UVC driver. However,
> > this might not be beneficial to all users. The buffer queue code in the
> > UVC driver
> > is USB-specific, and is thus smaller than video-buf. Users who currently
> > don't use video-buf would see their memory usage grow.
> >
> > Laurent Pinchart
>
> (I'll answer the other issues later)
Laurent Pinchart
--
Markus Rechberger
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