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Date:      Thu, 22 Jul 1999 21:17:39 -0700
From:      grady@xcf.berkeley.edu (Steven Grady)
To:        freebsd-smp@freebsd.org
Subject:   slow network reading with SMP
Message-ID:  <19990723044445.2C90A14FAE@hub.freebsd.org>

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We've got a SuperMicro P6DGU system (other specs: 2 450 MHz
Pentium IIIs, 256M mem, 18G SCSI, 25G UDMA) running 3.2-RELEASE.
The network card is a NetGear FA310TX Rev D1 (pn driver).

With an SMP kernel, TCP-based file transfers to the machine are very
slow (i.e.  50k/sec over a 100Mbit ethernet).  Transfers from the
machine are fine -- a couple megs per second.  After spending a lot of
time trying different things (swapping network cards, changing between
a switch and a hub, transferring to Windows vs. another BSD machine,
transferring via Samba vs. FTP), the one thing that made a difference
was to replace the kernel with a non-SMP version.  With the non-SMP
kernel, writes went up to 6 M/sec (depending on the protocol).
The only difference between the kernels was the deletion of the following
lines:
    options	SMP
    options	APIC_IO

Why is this happening?  And more importantly, what can we do to use
both processors while still keeping full network speed?  (Others in the
company have mentioned Linux -- I'd like to avoid that.)

	Steven
	grady@xcf.berkeley.edu

"When will I learn?  The answers to life's problems aren't at the
bottom of a bottle.  They're on TV!"


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