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    SubjectRe: [PATCH] nfs: fix congestion control
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    On Fri, 2007-01-19 at 18:57 +0100, Peter Zijlstra wrote:
    > On Fri, 2007-01-19 at 09:20 -0800, Christoph Lameter wrote:
    > > 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.
    >
    > Eeuh, right. Glad to have you around to remind how puny my boxens
    > are :-)
    >
    > > 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.
    >
    > Right, perhaps cap this to a max of 256M. That would allow 128 2M RPC
    > transfers, much more would not be needed I guess. Trond?

    That would be good as a default, but I've been thinking that we could
    perhaps also add a sysctl in /proc/sys/fs/nfs in order to make it a
    tunable?

    Cheers,
    Trond

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