This has been extensively explored, it is a hardware limitation, we have to use large buffers and need very low latency of the allocation (so have to use static ones). Most systems can handle this upon reboot, the chip is just not great at DMA buffer handling, so we can't use page size ones and dynamically allocate. It works most of the time, and in practice loading the module more than upon system load isn't probably done on a production system, so expected to happen sometimes if loading the module well after boot more than once.
Also the doc dir has some info in troubleshooting, about a setting to make the system allocate more non-fragmented memory in reserve to keep this from happening. Thanks, Chris On Mon, Apr 18, 2005 at 04:54:36PM -0400, D. Hugh Redelmeier wrote: > | From: D. Hugh Redelmeier <[EMAIL PROTECTED]> > | Date: Mon, 28 Mar 2005 20:26:58 -0500 (EST) > > | Summary: "modprobe ivtv" produces scarry messages and did not work. > See <http://sourceforge.net/mailarchive/message.php?msg_id=11308676> > > I applied current Fedora Core 3 updates, including a kernel update, > rebuilt ivtv-0.3.2p, installed it, and modprobed it. > > This time it worked. In particular, the following error did not show > up in dmesg output: > | Mar 28 18:05:36 redclaw kernel: ivtv: Allocate DMA stream 1 > | Mar 28 18:05:36 redclaw kernel: modprobe: page allocation failure. order:5, > mode:0xd0 > > I suspect that the key difference is that this time I did the modprobe > in a freshly booted system and that the previous time the system had > been running for a while. Running for a while could have caused > physical memory had become fragmented. > > Here are subequent allocation messages from the modprobe that worked: > ivtv: Registered v4l2 device, streamtype 2 minor 224 > ivtv: Create stream 2 using 40 52224 byte buffers 0 kbytes total > ivtv: Allocate stream 2 using 40 52224 byte buffers 2097152 kbytes total > ivtv: Registered v4l2 device, streamtype 3 minor 24 > ivtv: Create DMA stream 3 using 455 4608 byte buffers 0 kbytes total > ivtv: Allocate DMA stream 3 using 455 4608 byte buffers 2097152 kbytes > total > ivtv: Registered v4l2 device, streamtype 4 minor 64 > ivtv: Create stream 4 > ivtv: Allocate stream 4 > > Here's what leaves me unsettled. The failure was apparently for > allocating the scatter-gather array for stream 1. A scatter-gather > array should be small: about 12 bytes per page in the stream. Yet > the failed allocation was of order 5 -- 32 pages. That isn't a lot, > so it shouldn't be hard to find that much contiguous space. > > On the other hand, that suggests that a *lot* of pages are going to be > allocated to the stream: > 32*4096 / 12 = 10922 > 40 megabytes of RAM. Something seems wrong. > > Finally, I would point out that the driver did not fail gracefully. > If allocation fails, the driver should shut down cleanly, but it did > not. > > So there are a bunch of dangling ends with respect to my original > report. > > BTW, I got a private message from someone who had a similar problem. > I asked them to post to the list, but I don't think that they did. > That was the only response I've gotten. > > > ------------------------------------------------------- > This SF.Net email is sponsored by: New Crystal Reports XI. > Version 11 adds new functionality designed to reduce time involved in > creating, integrating, and deploying reporting solutions. Free runtime info, > new features, or free trial, at: http://www.businessobjects.com/devxi/728 > _______________________________________________ > ivtv-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/ivtv-devel -- --- Chris Kennedy / [EMAIL PROTECTED] Engineer KMOS-TV/KTBG-FM Broadcasting Services Department Central Missouri State University ------------------------------------------------------- This SF.Net email is sponsored by: New Crystal Reports XI. Version 11 adds new functionality designed to reduce time involved in creating, integrating, and deploying reporting solutions. Free runtime info, new features, or free trial, at: http://www.businessobjects.com/devxi/728 _______________________________________________ ivtv-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ivtv-devel
