Re: OMAPFB: CMA allocation failures

From: Tomi Valkeinen
Date: Thu Oct 24 2013 - 03:01:32 EST


On 24/10/13 00:59, ÐÐÐÐÐÐ ÐÐÐÐÑÑÐÐ wrote:
> Hi,
> I wonder if there is any progress on the issue? Do you need me to send more data? Or
> should I raise the issue with the CMA maintainer?

No, I haven't had time to look at this. And frankly, I don't even have
an idea what to look for if I can't reproduce it. The issue is not about
display, but DMA allocation, of which I know very little.

So yes, I suggest you try to discuss this with CMA/DMA people.


> Regards,
> Ivo
> >-------- ÐÑÐÐÐÐÐÐÐÐ ÐÐÑÐÐ --------
> >ÐÑÐÐÑÐÐ: Re: OMAPFB: CMA allocation failures
> >ÐÐ: Tomi Valkeinen
> >
> >
> > Hi Tomi,
> >
> >>I think we should somehow find out what the pages are that cannot be
> >>migrated, and where they come from.
> >>
> >>So there are "anonymous pages without mapping" with page_count(page) !=
> >>1. I have to say I don't know what that means =). I need to find some
> >>time to study the mm.
> >
> >I put some more traces in the point of failure, the result:
> >page_count(page) == 2, page->flags == 0x0008025D, which is:
> >PG_locked, PG_referenced, PG_uptodate, PG_dirty, PG_active, PG_arch_1, PG_unevictable
> >Whatever those mean :). I have no idea how to identify where those pages come from.
> >
> >>Well, as I said, you're the first one to report any errors, after the
> >>change being in use for a year. Maybe people just haven't used recent
> >>enough kernels, and the issue is only now starting to emerge, but I
> >>wouldn't draw any conclusions yet.
> >
> >I am (almost) sure I am the first one to test video playback on OMAP3 with DSP video
> >acceleration, using recent kernel and Maemo5 on n900 :). So there is high probability the
> >issue was not reported earlier because noone have tested it thoroughly after the change.
> >
> >>If the CMA would have big generic issues, I think we would've seen
> >>issues earlier. So I'm guessing it's some driver or app in your setup
> >>that's causing the issues. Maybe the driver/app is broken, or maybe that
> >>specific behavior is not handled well by CMA. In both case I think we
> >>need to identify what that driver/app is.
> >
> >What I know is going on, is that there is heavy fs I/O at the same time - there is
> >a thumbnailer process running in background which tries to extract thumbnails of all video
> >files in the system. Also, there are other processes doing various jobs (e-mail fetching, IM
> >accounts login, whatnot). And in addition Xorg mlocks parts of its address space. Of course
> >all this happens with lots of memory being swapped in and out. I guess all this is related.
> >
> >However, even after the system has settled, the CMA failures continue to happen. It looks like
> >some pages are allocated from CMA which should not be.
> >
> >>I wonder how I could try to reproduce this with a generic omap3 board...
> >
> >I can always reproduce it here (well, not on generic board, but I guess it is even better to
> >test in real-life conditions), so if you need some specific tests or traces or whatever, I
> >can do them for you.
> >
> >Regards,
> >Ivo
> >

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