Re: [RFC] Hugetlb demotion for x86

Re: [RFC] Hugetlb demotion for x86

[Christoph Lameter]

Seems that the code is not modifying x86 code but all code. 

An app should be getting an out of memory error and not a SIGBUS when 
running out of memory.

I thought we fixed the SIGBUS problems and were now reporting out of 
memory? If there still is an issue then we better fix out of memory 
handling. Provide a way for the app to trap OOM conditions?

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Re: [RFC] Hugetlb demotion for x86

[Dave Hansen]

On Thu, 2006-05-11 at 11:10 -0500, Adam Litke wrote:
> Yes, the SIGBUS issues are "fixed".  Now the application is killed
> directly via VM_FAULT_OOM so it is not possible to handle the fault from
> userspace.  For my libhugetlbfs-based fallback approach, I needed to
> patch the kernel so that SIGBUS was delivered to the process like in the
> days of old.

Maybe this could be off-by-default behavior that can be enabled with a
special mmap flag or madvise, or something similar.  It seems that apps
don't want to get SIGBUS for low memory.  But, if they have _asked_ for
it, perhaps they'd be a bit more willing.

(BTW, I fixed the bogus linux-mm cc, finally ;)

-- Dave

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