memtest help

memtest help

[Bojan Prtvar]

Hello everyone,

I need to test all RAM cells on a linux ARM embedded system. My use case 
is very similar to the one described in [1] expect the fact I also have 
strong requirements on minimizing the boot time impact.
Instead of doing that from the bootloader, I decided to evaluate the 
linux memtest feature introduced with [2].

My questions are:

1)
Does the  early_memtest() as called in [3] really covers *all* RAM cells?

2)
As memtest happens very early in boot stage, what primitives I can use 
to measure duration of early_memtest()? Are there any known heuristics? 
I need to test ~2GB of RAM.
This is my major concern.

3)
It seems reasonable to expose the number of detected bad cells to user 
space. I was thinking about sysfs. Are the patches welcomed?

[1]
http://www.linuxforums.org/forum/newbie/173847-how-do-memory-ram-test-when-linux-running.html
[2]
http://lkml.iu.edu/hypermail/linux/kernel/1503.1/00566.html
[3]
http://lxr.free-electrons.com/source/arch/arm/mm/init.c#L291

Thanks,
Bojan

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Re: memtest help

[Vladimir Murzin]

On 28/04/16 17:42, Bojan Prtvar wrote:
> Hello everyone,
> 
> I need to test all RAM cells on a linux ARM embedded system. My use case
> is very similar to the one described in [1] expect the fact I also have
> strong requirements on minimizing the boot time impact.
> Instead of doing that from the bootloader, I decided to evaluate the
> linux memtest feature introduced with [2].
> 
> My questions are:
> 
> 1)
> Does the  early_memtest() as called in [3] really covers *all* RAM cells?

No.

> 
> 2)
> As memtest happens very early in boot stage, what primitives I can use
> to measure duration of early_memtest()? Are there any known heuristics?
> I need to test ~2GB of RAM.
> This is my major concern.

Stopwatch?

> 
> 3)
> It seems reasonable to expose the number of detected bad cells to user
> space. I was thinking about sysfs. Are the patches welcomed?
> 

$ dmesg | grep "bad mem"

Cheers
Vladimir

> [1]
> http://www.linuxforums.org/forum/newbie/173847-how-do-memory-ram-test-when-linux-running.html
> 
> [2]
> http://lkml.iu.edu/hypermail/linux/kernel/1503.1/00566.html
> [3]
> http://lxr.free-electrons.com/source/arch/arm/mm/init.c#L291
> 
> Thanks,
> Bojan
> 
> -- 
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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> 
> 

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