[pvrusb2] hauppage hvr-1900 on raspberry pi

[Felix Lighter]

I'm glad that Ethernet helped the situation.
Beware USB - it's also notorious for aggressively interrupting the CPU.
480Mbps USB2 comes at a high price, CPU-wise. And as you point out,
it's already busy capturing video.

I would definitely suggest looking into NFS, since you should be able
to lighten the CPU load even further by increasing the write buffer
size (in the mount options). Take a look and see whether Samba also
offers any options for tuning network usage / bandwidth.

Cheers,
FL

On 7 June 2012 15:43, Emmanuel Touzery <etouzery at gmail.com> wrote:
> Hello,
>
>  Thanks for a lot for the tip. I tried quickly with a SMB share which I
> already had setup and... yes it seems better! Although I really can't
> believe it, it does seem to help. I'm glad you give me a plausible
> explanation with DMA though, because that's the last thing I was expecting.
> Especially since my network is not wired and though it's plugged using
> ethernet on the pi, it reaches my computer through wifi.
>
>  I'll try more. I didn't try much with USB keys too because I measured a
> slightly lower throughput than with the SD card and I read that on the pi,
> the throughput for USB+ethernet is shared. I figured, since USB is already
> busy receiving the data from the video capture device, better save on the
> SD... but apparently not.
>
>  But really I can't conclude much until I test more. The first tests seems
> to say network>usb>sd. but even on network I've seen a skip. Though it's on
> a non-preempt kernel and without any sort of buffering (eg flywheel or
> fifo), nor nice or chrt.
>
>  Anyway, it seems there's not much hope of configuring something
> differently on the driver or the kernel, so for now I'll focus on where to
> save: SD, network, usb, with or without FIFO and so on. And maybe also NFS
> vs SMB, if SMB doesn't always cut it. Definitely network appears the most
> promessing option for now! So thanks again for the tip!
>
> emmanuel
>
> On Wed, Jun 6, 2012 at 10:27 PM, Felix Lighter <felix.lighter at gmail.com>wrote:
>
>> Saving to a network share (e.g. NFS with intermediate block size)
>> might perform better.
>> The Ethernet port is likely to be much better served by the CPU's DMA
>> facilities than its SD interface is.
>>
>> Cheers, FL
>>
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