On 28 Apr 2010, at 14:26, erik quanstrom wrote:
Could round-trip times be adding up? Does 9p do one file at once
strictly?
i think you mean, does 9p have 1 outstanding message.
it does not. 9p supports having as many outstanding
messages as one wishes. if you do a pread(2), the kernel
will only maintain a single outstanding message for you.
fcp is a quick hack around this. by keeping n threads
each doing a read, you can keep n messages outstanding.
there is nothing (save complexity) preventing the kernel
from keeping multiple outstanding 9p messages.
this is the technique aoe uses to overcome drive latency,
which — even for enterprise slc ssds — can be considerable
in the worst case (~500ms).
- erik
Yeah, if I understand right that is what I meant. Good to know, but
I'm back to the drawing board on why 9p is sometimes so very much
slower than transferring the equivalent files in a tar file over http.
Maybe fcp should be used with a large number of threads? :s
--
Simplicity does not precede complexity, but follows it. -- Alan Perlis
