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

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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