From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <7b628fbb325ea03705615fca437c1735@collyer.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] NOW it's like lightning
From: Geoff Collyer <geoff@collyer.net>
Date: Tue,  8 Jun 2004 18:56:19 -0700
In-Reply-To: <40C66BDC.6070301@yahoo.com>
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Some IDE disks or controllers have buggy DMA implementations, so DMA
is off by default to err on the side of caution.

The performance of your Ethernet interface probably depends mostly on
the quality of the card.  Worst case is probably the old NE2000, which
I think was all programmed I/O, no real DMA (the PC world has funny
definitions of `DMA').  The worst modern-day case is likely the
RTL8139, which is pretty dumb.  Best cases are probably the Intel and
National Semiconductor controllers, which maintain ring buffers of
incoming and outgoing packets and use DMA to transfer them.  Microsoft
may have information not available to the general public, or they may
just throw more CPU time at making dumb interfaces run fast.

Of course, you're probably not exercising the raw Ethernet interface,
so there are also TCP and IP speeds to consider.

How are you copying the data in question, using which version of IP (4
or 6), using what Ethernet interface on Plan 9, at what link speed?