[Nottingham] Random Windows-y network-y/file IO-y question

[Martin]

On 31/10/13 15:08, Jason Irwin wrote:
> Is there some kind of Windows network bandwidth limit per thread of
> execution? i.e. per connection from the same client.
> And I mean over and above what the firewalls etc might be imposing.
> 
> Or is there some per limit on file IO per thread?
> 
> Something tells me there is, but for the friggin' life of me I can find
> the sodding documentation.
> 
> I did stumble across SMB multichannel docs which look interesting.  Will
> have to see if Samba support that in a bit.

On the networking side, there is a physical limit imposed by the link
latency for getting ack packets back and the max number of data packets
allowed in flight... Windows has had problems with that in the past as
networks speed has increased whilst we are still stuck on the imposed
'industry standard' 1500 max packet size. There's been a few
work-arounds but you are still stuffed if you are suffering high latency.

And the latency can add up surprisingly quickly when traversing multiple
strings of VPNs and multiple IO buffers... Or traversing multiple VMs
that do not have a physical core all to themselves...


Don't know about Windows limits at that level. Not had to look there for
a long time.


Rambling on:

Or... You've exceeded your Virginal arbitrary quota and you're now
considered no longer virginal... ;-)

Try a speed test?...


Also note that Windows is still not truly preemptive multithreaded...


Or more simply:

Fragmented disks?
Or multiple streams rattling the heads around?
Or choked on raid overhead?
Or choked on encryption overhead?
Or a choked switch?
Or sleepy VMs?
Or...

Break the problem down into smaller segments to test?

All on LAN or WAN?

Or if on WiFi then you are strangled anyway...


Good luck,
Martin

-- 
- ------------------ - ----------------------------------------
-    Martin Lomas    - OpenPGP (GPG/PGP) Public Key: 0xCEE1D3B7
- martin @ ml1 co uk - Import from   hkp://subkeys.pgp.net   or
- ------------------ - http:// ml1 .co .uk/martin_ml1_co_uk.gpg