Re: A question about the bandwith?

Michel Bardiaux wrote:

Johnny Strom wrote:

Hello

I have setup a system that captures jpeg pictures from four v4l devices it's 4 Hercules smart TV cards.

And first I did a script with streamer that captures one after the other

then I taught that I could capture from all four TV cards in paralell, so my question is the bandwith enough on the PCI bus to start a capture of four .jpeg files from four cards at the same time and then sleep for one second after the capture?

The system is a Celeron 2.2 Ghz and lspci looks like this:

[snip]

Why I am asking this is becouse after I did change the script so did I start getting kernel oopses like the ones below, so could the tree oopses below be becouse of a badblocks on the swap or memory related or becouse of to much data on the pci bus at the same time?

I did try to cahnge the memory but I still get ooopses.



OOPS 1:

Unable to handle kernel paging request at virtual address 74767679
c013029c

How is your /etc/modules? How is /proc/meminfo?

I ask because I use 2 Hercules SmartTV for 706x576x25fps YUV420P grabbing (for MPEG), on a 128MB P4 2.4GHz. I discovered that by default the bttv driver for Hercules (card=100) allocates not 2 but 5 gbuffers. If you use RGBA, that makes 706x576x5(gbuffers)x4(bytes/pixel)x4(cards) or 32MB reserved in the kernel for gbuffers. If you are marginal in memory, it could cause problems in kernel paging.

Try something like bttv card=100,100,100,100 gbuffers=2 in /etc/modules. For JPG grabbing, if 40msec jitter is acceptable, it might even be possible to use only 1 gbuffer.

My /etc/modules.conf is like this:


cat /etc/modules.conf
#alias eth0 e100
#alias usb-controller ehci-hcd
#alias sound-slot-0 i810_audio

#alias usb-controller1 usb-uhci
# i2c
alias char-major-89 i2c-dev
options i2c-core i2c_debug=1
options i2c-algo-bit bit_test=1

# bttv
alias char-major-81 bttv
options bttv card=100,100,100,100 radio=1,1,1,1
options tuner debug=0
alias eth0 e100

And /proc/meminfo
        total:    used:    free:  shared: buffers:  cached:
Mem:  260653056 256053248  4599808        0 19783680 157757440
Swap:        0        0        0
MemTotal:       254544 kB
MemFree:          4492 kB
MemShared:           0 kB
Buffers:         19320 kB
Cached:         154060 kB
SwapCached:          0 kB
Active:         126700 kB
Inactive:        90872 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       254544 kB
LowFree:          4492 kB
SwapTotal:           0 kB
SwapFree:            0 kB


Swap is off at the moment it was about 512MB when I got the oopses,

Thanks I will repport back later how it went.


Cheers Johnny