Re: Different NFSSVC_MAXBLKSIZE for udp and tcp clients?

[Greg Banks <gnb@melbourne.sgi.com>]

"Lever, Charles" wrote:
> 
> here's a vote for leaving these values variable rather than
> fixed on the server side.  48KB maximum for UDP is great on
> a clean network, but some folks would probably prefer setting
> it to 8KB to ensure clients on more realistically congested
> networks retain reasonable UDP performance.

Agreed.

> is there any evidence to show that a 4MB TCP maximum will
> have benefits over something smaller, like say 1MB ?  

None at all on Linux.  I mention that specific number only
because it's the hardcoded maximum on IRIX.

However there is evidence that 8K isn't enough.  In particular,
it's smaller than an Altix client's PAGE_CACHE_SIZE so all writes
between two Altix boxes go synchronous.

> [...] there's probably a sweet spot where the sum
> of both per-op and per-byte costs reach a minimum.  

Yes.

> as
> far as i can tell that value is around 16KB in the current
> Linux client implementations.

The value will be higher for Altix clients and servers, which
have more RAM, CPU, and larger pages than the machines you're
probably thinking of.

Greg.
-- 
Greg Banks, R&D Software Engineer, SGI Australian Software Group.
I don't speak for SGI.


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