Re: Getting rid of SHMMAX/SHMALL ?

On Thu, Aug 04, 2005 at 03:49:37PM -0700, Chen, Kenneth W wrote:

Andi Kleen wrote on Thursday, August 04, 2005 6:24 AM

quoted

I think we should just get rid of the per process limit and keep
the global limit, but make it auto tuning based on available memory.
That is still not very nice because that would likely keep it < available 
memory/2, but I suspect databases usually want more than that. So
I would even make it bigger than tmpfs for reasonably big machines.
Let's say

if (main memory >= 1GB)
	maxmem = main memory - main memory/8 

This might be too low on large system.  We usually stress shm pretty hard
for db application and usually use more than 87% of total memory in just
one shm segment.  So I prefer either no limit or a tunable.

With large system you mean >32GB right?

I think on a large systems some tuning is reasonable because they likely
have trained admins. I'm more worried on reasonable defaults for the
class of systems with 0-4GB

The /8 was to account for the overhead of page tables and mem_map and
leave some other memory for the system, but you're right it might be less 
with hugetlbfs.

-Andi
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