Linked by Thom Holwerda on Wed 29th Aug 2007 00:28 UTC, submitted by diegocg
Windows Robert Love, a famous Linux kernel hacker, has written a blog entry with his thoughs on the recently posted Vista's network slowdown issue and the explanation given by Mark Russinovich: "Unlike DPCs, however, the Linux parallel does not consume nearly half of your CPU. There is no excusable reason why processing IP packets should so damagingly affect the system. Thus, this absolutely abysmal networking performance should be an issue in and of itself, but the Windows developers decided to focus on a secondary effect."
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Latency and network.
by philicorda on Wed 29th Aug 2007 15:58 UTC
philicorda
Member since:
2005-12-31

This reminds me of a Microsoft paper called:
"The Problems You're Having May Not Be the Problems You Think You're Having"

It was written in 1998 and was a study of the problems with handling low latency audio, video etc tasks on NT kernel based operating systems.

It has an interesting paragraph:

"Another commonly held view is that Ethernet input packet processing is a problem. Yet we tested many of the most popular 10/100 Ethernet cards receiving full rate 100Mbit point-to-point TCP traffic up to user space. The cards we tested were the Intel EtherExpress Pro 100b, the SMC EtherPower II 10/100, the Compaq Netelligent 10/100 Tx, and the DEC dc21x4 Fast 10/100 Ethernet. The longest observed individual DPC execution we observed was only 600 Ás, and the longest cumulative delay of user-space threads was approximately 2ms. Ethernet receive processing may have been a problem for dumb ISA cards on 386/20s, but it's no longer a problem for modern cards and machines."

So why did Microsoft need to fix something that was not broken?

Reply Score: 1

RE: Latency and network.
by n4cer on Wed 29th Aug 2007 19:06 in reply to "Latency and network."
n4cer Member since:
2005-07-06

You're assuming that those results are still relevant. Windows' architecture has changed signifigantly in 9 years, as have NICs and NIC drivers (and the care taken in writing them). More processing is done in software on the low-end because it's more cost effective, not unlike with most modems today vs. their more expensive hardware counterparts. Greater driver dependance leads to greater variances between driver versions. The driver could easily harm performance with long DPC latencies, wheras a different driver improves performance by shortening such latences. Likewise, the driver's configuration can also impact performance.

Edited 2007-08-29 19:10

Reply Parent Score: 4

RE: Latency and network.
by seanwal111111 on Mon 3rd Sep 2007 03:21 in reply to "Latency and network."
seanwal111111 Member since:
2007-09-03

Thank you for that interesting 1998 quotation about 100 mb ethernet. Today 1000 mb ethernet transfers in XP on one of today's machines consumes nearly half of the CPU, but running MP3 audio concurrently does NOT produce glitches in the audio.

Reply Parent Score: 1