Re: [PATCH] nfs: fix congestion control

[Christoph Lameter]

On Fri, 19 Jan 2007, Peter Zijlstra wrote:

> +	/*
> +	 * NFS congestion size, scale with available memory.
> +	 *

Well this all depends on the memory available to the running process.
If the process is just allowed to allocate from a subset of memory 
(cpusets) then this may need to be lower.

> +	 *  64MB:    8192k
> +	 * 128MB:   11585k
> +	 * 256MB:   16384k
> +	 * 512MB:   23170k
> +	 *   1GB:   32768k
> +	 *   2GB:   46340k
> +	 *   4GB:   65536k
> +	 *   8GB:   92681k
> +	 *  16GB:  131072k

Hmmm... lets say we have the worst case of an 8TB IA64 system with 1k 
nodes of 8G each. On Ia64 the number of pages is 8TB/16KB pagesize = 512 
million pages. Thus nfs_congestion_size is 724064 pages which is 
11.1Gbytes?

If we now restrict a cpuset to a single node then have a 
nfs_congestion_size of 11.1G vs an available memory on a node of 8G.
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