Re: high latency with TCP connections
From: Rick Jones <hidden>
Date: 2006-08-31 19:40:50
Kelly Burkhart wrote:
On 8/30/06, David Miller [off-list ref] wrote:quoted
From: Stephen Hemminger <redacted>quoted
Expecting any performance with one byte write's is silly.This is absolutely true. TCP_NODELAY can only save you when you are sending a small amount of data "in aggregate", such as in an SSH or telnet session, whereas in the case being shown here a large amount of data is being sent in small chunks which will always get bad performance.The word performance in this list seems to always mean 'throughput'. It seems though that there could be some knob to tweak for those of us who don't care so much about throughput but care a great deal about latency.
IIRC Apart from interactions with Nagle (TCP_NODELAY) or the mixing of packet and byte-based congestion control and avoidance heuristics, there really isn't much of anything else to tweak in TCP. If it can send data, it sends data. Where there _is_ a knob to turn these days might be down with the drivers and their NICs' use of interrupt coalescing: ftp://ftp.cup.hp.com/dist/networking/briefs/nic_latency_vs_tput.txt rick jones