Subject: Re: [RFC] powerpc/hugetlb: Add warning message when gpage allocation request fails

From: Nishanth Aravamudan <[email-masked]>
Date: Mon, 14 Sep 2015 09:24:26 -0700

On 14.09.2015 [18:59:25 +0530], Aneesh Kumar K.V wrote:
> Anshuman Khandual <[email-masked]> writes:
> 
> > When a 16GB huge page is requested on POWER platform through kernel command
> > line interface, it silently fails because of the lack of any gigantic pages
> > on the system which the platform should have communicated through 16GB memory
> > blocks in the device tree during boot time. For example
> >
> > [    0.480940] HugeTLB registered 16 GB page size, pre-allocated 0 pages
> > [    0.480945] HugeTLB registered 16 MB page size, pre-allocated 16 pages
> >
> > This adds a warning message during alloc_bootmem_huge_page request both on
> > book3e and book3s powerpc platforms. After this change
> >
> > [    0.000000] Gigantic HugeTLB page not available
> > [    0.473417] HugeTLB registered 16 GB page size, pre-allocated 0 pages
> > [    0.473423] HugeTLB registered 16 MB page size, pre-allocated 16 pages
> 
> 
> That info is already part of the second line isn't it ? ie
> 
> [    0.473417] HugeTLB registered 16 GB page size, pre-allocated 0 pages
> 
> pre-allocated 0 pages indicate we didn't allocate anything. So why do we
> need to add more details fo kernel output ?

Agreed, the '0 pages' message indicates we failed to pre-allocate any
pages. The 'pre-allocate' messages are specifically about the kernel
command-line requests for hugepages.

Not sure I understand the motivation for this?

-Nish