awalls at radix
Nov 5, 2009, 3:09 PM
Post #2 of 2
On Thu, 2009-11-05 at 09:18 -0600, Steve Gunther wrote:
> I am modifying my ivtv settings to increase buffer size. I am using
> the following string;
> options ivtv enc_yuv_buffers=8 enc_mpg_buffers=48 enc_vbi_buffers=16
> So by my math 8MB YUV + 48M MPG + 16M VBI + 960k = ~73M per tuner.
> I have four tuners...
> After boot I;
> sudo rmmod ivtv
> My memory usage is at 435672k used. After I;
> sudo modprobe ivtv
> My memory usage is 1029156k used, for a difference of 593484k or ~148M
> per card.
> As far as the modino states the defaults should be So by my math 2MB
> YUV + 4M MPG + 1M VBI + 320k = ~7M per tuner.
> With no modifier string my memory usage is 16M per card.
> Any idea why my memory usage would be approximately double the
> assigned buffer size?
Likely because you don't have a hardware IOMMU, and thus the linux
kernel is using it's "software" IO MMU and allocating DMA bounce
That's just a guess of course.
If you are upping the memory for buffers because you are worried that
you CPU can't keep up, be aware that I believe software bounce buffers
require the CPU to do memcpy()'s of the contents of the buffers to get
them to the ivtv driver.
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