Date: Wed, 31 Jan 2001 12:22:13 -0800
From: Mike Smith <msmith@freebsd.org>
To: Dag-Erling Smorgrav <des@ofug.org>
Cc: Dan Nelson <dnelson@emsphone.com>, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp>, arch@FreeBSD.ORG
Subject: Re: Bumping up {MAX,DFLT}*PHYS (was Re: Bumping up {MAX,DFL}*SIZ in i386)
Message-ID: <200101312022.f0VKMDW00902@mass.dis.org>
In-Reply-To: Your message of "31 Jan 2001 21:07:45 %2B0100." <xzphf2fo57y.fsf@flood.ping.uio.no>
next in thread | previous in thread | raw e-mail | index | archive | help
> Dan Nelson <dnelson@emsphone.com> writes:
> > On a similar note, is there any reason for us to have DFLTPHYS at 64k
> > anymore? With the insane interface speeds of SCSI and ATA devices
> > nowadays, you can easily hit 600 I/Os per second on sequential reads
> > (40MB/sec, 64K per I/O). Would anything break if MAXPHYS/DFLTPHYS was
> > bumped to say, 1mb?
>
> I think so; we can't do DMA transfers larger than 64k (128k in word
> mode) - at least for ISA devices, I don't know much about PCI.
It's 128K right now, actually. The problem is that a lot of older
devices have limits which cap them at 64K. (Typically, 16-bit bytecount
registers, or 16- or 17-slot scatter/gather tables.)
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200101312022.f0VKMDW00902>