[gentoo-amd64] how to track down strange bug

[gentoo-amd64] how to track down strange bug

[Florian D.]

Hi,
I have been hitting by a bug for ages, which I want to get rid of 
eventually ;)

It is not possible for me to watch TV via xawtv, while doing IO 
intensive tasks in the background. In the majority of cases, it 
suffices to copy a, say, 50MB file from my USB-stick to the harddisk 
to freeze my amd64 machine (but, funny enough, the sound is playing 
further on).

Since I suppose that people don´t have any clue what its going on 
here, I just want to ask, what is the best way to debug this? There is 
nothing in the log file.

TIA
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Re: [gentoo-amd64] how to track down strange bug

[Peter Davoust]

As in nothing at all in the log file, or nothing unusual in the log
file? Also, how much Ram do you have? Could you try doing ps aux and
then copying the 50MB and watching what proceses come up when it
crashes? Maybe it's an X issue, because it seems like the gui freezes
but the rest doesn't. Does the file eventually copy all the way? Just
sort of thinking out loud there.

-Peter

On 10/18/06, Florian D. <flockmock@gmx.at> wrote:
> Hi,
> I have been hitting by a bug for ages, which I want to get rid of
> eventually ;)
>
> It is not possible for me to watch TV via xawtv, while doing IO
> intensive tasks in the background. In the majority of cases, it
> suffices to copy a, say, 50MB file from my USB-stick to the harddisk
> to freeze my amd64 machine (but, funny enough, the sound is playing
> further on).
>
> Since I suppose that people don´t have any clue what its going on
> here, I just want to ask, what is the best way to debug this? There is
> nothing in the log file.
>
> TIA
> --
> gentoo-amd64@gentoo.org mailing list
>
>

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[gentoo-amd64] Re: how to track down strange bug

[Duncan]

"Florian D." <flockmock@gmx.at> posted 4536AB1E.80004@gmx.at, excerpted
below, on  Thu, 19 Oct 2006 00:30:54 +0200:

> I have been hitting by a bug for ages, which I want to get rid of
> eventually ;)
> 
> It is not possible for me to watch TV via xawtv, while doing IO intensive
> tasks in the background. In the majority of cases, it suffices to copy a,
> say, 50MB file from my USB-stick to the harddisk to freeze my amd64
> machine (but, funny enough, the sound is playing further on).

No way to say this is what you are experiencing without knowing more
details than you could have provided in a first post on the subject, but
in many cases, such problems are due to running the wrong or a generic
hard drive (PATA/SATA/SCSI whatever) chipset driver, or perhaps more
often, a bunch of such drivers -- I've seen as many as eight different
drivers loaded on the same machine, where only one or possibly two would
normally be used.  Get the wrong one loaded or loaded before the right
one so the right one has nothing to grab, and you don't get DMA activated,
and the CPU must be much more intimately involved in every I/O
transaction, which also goes much slower.

So make sure you have the right one running, and aren't loading a bunch of
others, and that DMA is active (merge hdparm and read the manpage).

The problem in this case would be slow non-DMA I/O interfering with video
DMA as well.

The problem could also be a non-optimally configured xorg or extensions,
or selecting a type of video transfer that your particular video hardware
and xorg driver don't support.

Finally, flaky memory, overclocking and/or overheating, or an unstable
power supply chain (from the wall outlet thru the UPS if you have one,
thru the PSU) can do it.  Of course, these are likely to show up in other
areas as well, such as when merging on Gentoo.

I've had all those problems at one time or another.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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Re: [gentoo-amd64] Re: how to track down strange bug

[Florian D.]

Duncan wrote:
> So make sure you have the right one running, and aren't loading a bunch of
> others, and that DMA is active (merge hdparm and read the manpage).
that is already the case.
> 
> The problem in this case would be slow non-DMA I/O interfering with video
> DMA as well.
> 
> The problem could also be a non-optimally configured xorg or extensions,
> or selecting a type of video transfer that your particular video hardware
> and xorg driver don't support.
hmm.. NVIDIA card with nv driver, but I'll have a look.
> 
> Finally, flaky memory, overclocking and/or overheating, or an unstable
> power supply chain (from the wall outlet thru the UPS if you have one,
> thru the PSU) can do it.  Of course, these are likely to show up in other
> areas as well, such as when merging on Gentoo.
my hardware should be ok. thank you for your commentary, but I think 
it is a kernel issue. perhaps I can find one, which does not show the 
issue and then start a bisect or something, or is there any other 
method to track this down?
> 
> I've had all those problems at one time or another.
would be boring without it, no? ;)
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Re: [gentoo-amd64] Re: how to track down strange bug

[Rob Lesslie]

My Dad has a PCI Nebula DigiTV card, which gives the following problem
in Windows and Linux:

When using the IDE disk and watching TV, there is no problem.  When
using either of the SATA disks heavily however, the TV becomes
unwatchable and exhibits the symptoms described above.

I have always but this down to a conflict between the SATA controller
and the DigiTV card - possibly and IRQ conflict but don't hold me to
that.

Sorry that I can't provide exact specs for the hardware at the moment
(I am at work and I am not quite sad enough to remember all the specs
for his machine) but I *THINK* it is a Gigabyte motherboard with both
a VIA and a Promise SATA controller.  I am not sure which SATA
controller gives the problem, but it is only one of them.  Machine is
a socket 739 AMD64 3000+ with 2 x 512Mb RAM.

-- 
Rob Lesslie
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[gentoo-amd64] Re: how to track down strange bug

[Duncan]

"Florian D." <flockmock@gmx.at> posted 45374742.4010604@gmx.at, excerpted
below, on  Thu, 19 Oct 2006 11:37:06 +0200:

>> I've had all those problems at one time or another.
> would be boring without it, no? ;)

Indeed. =8^)  Part of the reason Linux (and computers in general) remain
interesting to me is the challenge of figuring out what went wrong and
fixing it.  I don't find my freezer or microwave near this interesting,
because they "just work". =8^)  It'd be like watching grass grow or paint
dry.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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Re: [gentoo-amd64] Re: how to track down strange bug

[Neil Bothwick]

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On Thu, 19 Oct 2006 20:51:51 +0000 (UTC), Duncan wrote:

> Indeed. =8^)  Part of the reason Linux (and computers in general) remain
> interesting to me is the challenge of figuring out what went wrong and
> fixing it.  I don't find my freezer or microwave near this interesting,
> because they "just work". =8^)  It'd be like watching grass grow or
> paint dry.

My microwave stopped working recently, just out of warranty. I had great
fun searching the web for info then pulling the microwave to bits to
diagnose the fault. I was most disappointed to find that a DIY repair of
the problem was too unsafe to consider :(


-- 
Neil Bothwick

Secret hacker rule #11: hackers read manuals.

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[gentoo-amd64] Re: how to track down strange bug

[Duncan]

Neil Bothwick <neil@digimed.co.uk> posted
20061019234855.64a8d770@krikkit.digimed.co.uk, excerpted below, on  Thu,
19 Oct 2006 23:48:55 +0100:

> My microwave stopped working recently, just out of warranty. I had great
> fun searching the web for info then pulling the microwave to bits to
> diagnose the fault. I was most disappointed to find that a DIY repair of
> the problem was too unsafe to consider :(

I had to buy a new one about a year ago as well.  I had actually pulled
mine apart before to reset an overheat switch, but the fan/wave-spreader
was simply old and had started sticking, and this time the thing
overheated and melted some of the plastic mountings.  At about 15 years
old, I figured it was time to by a new one anyway, and I was right.  The
new one is far more efficient and more convenient to use, and was
surprisingly cheap.  I should have thrown the old one away 2-3 years
earlier, tho it did still work and wasn't unsafe, just inefficient and
more work to continue to use than it was worth, given the cost of a new
one.

At the cost any more, like so much these days, microwave ovens are
essentially disposable -- simply not worth repairing.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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Re: [gentoo-amd64] Re: how to track down strange bug

[Neil Bothwick]

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On Fri, 20 Oct 2006 10:41:47 +0000 (UTC), Duncan wrote:

> At the cost any more, like so much these days, microwave ovens are
> essentially disposable -- simply not worth repairing.

Except mine was an expansive combination oven :(


-- 
Neil Bothwick

What do you do when you see an endangered animal eating an endangered
plant?

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[gentoo-amd64] Re: how to track down strange bug

[Duncan]

Neil Bothwick <neil@digimed.co.uk> posted
20061020120941.550516d5@hactar.digimed.co.uk, excerpted below, on  Fri, 20
Oct 2006 12:09:41 +0100:

> Except mine was an expansive combination oven :(

In that case, yeah, it's probably worth repairing if possible.  Too bad
it wasn't, then. =8^(

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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Re: [gentoo-amd64] Re: how to track down strange bug

[Paul de Vrieze]

Neil Bothwick wrote:
> On Fri, 20 Oct 2006 10:41:47 +0000 (UTC), Duncan wrote:
> 
>> At the cost any more, like so much these days, microwave ovens are
>> essentially disposable -- simply not worth repairing.
> 
> Except mine was an expansive combination oven :(

How can you expand combination ovens ;-) ? In general combination ovens 
don't work either way. The microwave can't really handle the heat. The 
oven is too cramped to bake anything decent in it. We specifically opted 
for two devices for that reason.

Paul
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Re: [gentoo-amd64] Re: how to track down strange bug

[Rob Lesslie]

> How can you expand combination ovens ;-) ? In general combination ovens
> don't work either way. The microwave can't really handle the heat. The
> oven is too cramped to bake anything decent in it. We specifically opted
> for two devices for that reason.

Convergence in electronic devices is not always the answer :)
-- 
Rob Lesslie
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Re: [gentoo-amd64] Re: how to track down strange bug

[Neil Bothwick]

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On Fri, 20 Oct 2006 17:02:47 +0200, Paul de Vrieze wrote:

> > Except mine was an expansive combination oven :(  
> 
> How can you expand combination ovens ;-) ? 

With difficulty :)

> In general combination ovens 
> don't work either way. The microwave can't really handle the heat. The 
> oven is too cramped to bake anything decent in it.

That's why you expand it ;-)

Seriously, even if grossly off-topic, although not large enough for a
family meal, the oven is quite big enough for mid-week duties. I can't
afford to ring for pizza every night :)


-- 
Neil Bothwick

Q: How many builders does it take to change a light bulb?
A: "If only it was just the light bulb......we'll have to replace the
ceiling and..........."

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Re: [gentoo-amd64] how to track down strange bug

[Paul de Vrieze]

Florian D. wrote:
> Hi,
> I have been hitting by a bug for ages, which I want to get rid of 
> eventually ;)
> 
> It is not possible for me to watch TV via xawtv, while doing IO 
> intensive tasks in the background. In the majority of cases, it suffices 
> to copy a, say, 50MB file from my USB-stick to the harddisk to freeze my 
> amd64 machine (but, funny enough, the sound is playing further on).

It is quite important that you use dma accelerated tv out. Especially 
with xawtv as it doesn't do postprocessing this should work until you 
saturise your pci bus. The freezing thing however suggests that dma is 
not enabled for your harddisk which is an even bigger performance issue. 
Make sure you have the right drivers in your kernel, or loaded as module.

Paul
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