Re: [PATCH 0/4] Demand faunting for huge pages

["Ray Bryant" <raybry@mpdtxmail.amd.com>]

On Wednesday 17 August 2005 19:33, David Gibson wrote:

>
> Strict accounting leads to nicer behaviour in some cases - you'll tend
> to die early rather than late - but it seems an awful lot of work for
> a fairly small improvement in behaviour.
>

The last time we went around on this (April 2004?) Andrew thought that adding 
demand allocation for hugetlb pages without strict accounting was effectively 
an ABI change -- in the current approach the mmap() will fail if you ask for 
too many hugetlb pages whilst in the demand fault approach you will get 
SIGBUS at a later point in time.   At one time this was considered serious 
enough to fix.

Andy Whitcroft provided some code for the patch that Ken and I did back in
April 2004 time frame.   I can't find that one but the following patch from
Christoph Lameter appears to be the code.  The idea is that at mmap() time
a strict reservation is made that guarantees the necessary number of 
hugetlb pages is available. 

http://marc.theaimsgroup.com/?l=linux-kernel&m=109842250714489&w=2

-- 
Ray Bryant
AMD Performance Labs                   Austin, Tx
512-602-0038 (o)                 512-507-7807 (c)

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