[Hackage] #447: do parallel builds

Thomas DuBuisson thomas.dubuisson at gmail.com
Sat Jan 17 14:26:52 EST 2009

Among other potential issues, I think he's saying that the TCP window
size closes for any one connection (because the RTT is high, ACKs
don't come often enough).  Therefore, multiple downloads (multiple TCP
connections) can provide a boost even when going to the same server.

I've heard of this before and at the time advocated SCTP - not sure if
that's a good option here.


On Sat, Jan 17, 2009 at 5:16 PM, Duncan Coutts
<duncan.coutts at worc.ox.ac.uk> wrote:
> On Wed, 2009-01-14 at 00:09 +0900, Curt Sampson wrote:
>> On 2009-01-10 16:01 -0000 (Sat), dunacn wrote:
>> >  Also downloads seem to be serialised, again because there is probably
>> >  little benefit to making multiple connections to the same server.
>> You evidently don't live in Japan. :-)
>> On high-bandwidth, high-latency links (e.g., Tokyo to a server in
>> NYC, which has well over 200 ms latency just due to the distance) TCP
>> doesn't work so well unless both sides are very well tuned for high
>> bandwidth-latency products. I'm generally on a 100 Mbps fibre connection
>> in Tokyo (it's the standard home or small office connection here), and
>> parallel downloads are a very happy thing; in some circumstances I can
>> run a dozen downloads in parallel, without any individual one being
>> slower than it would be running alone.
> Presumably to different servers though right?
> I was also under the impression that most web servers kind of frowned on
> more than one or two connections from the same client and some would
> take active measures to prevent it.
> Duncan
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