Date: Sat, 03 Feb 2001 14:03:49 -0700
From: "Justin T. Gibbs" <gibbs@scsiguy.com>
To: Matt Dillon <dillon@earth.backplane.com>
Cc: Mike Smith <msmith@FreeBSD.ORG>, Dag-Erling Smorgrav <des@ofug.org>, 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: <200102032103.f13L3nO55354@aslan.scsiguy.com>
In-Reply-To: Your message of "Wed, 31 Jan 2001 14:08:29 PST." <200101312208.f0VM8Tm17958@earth.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> And, finally, while large I/O's may seem to be a good idea, they can > actually interfere with the time-share mechanisms that smooth system > operation. Large I/Os, while interesting for disks, are often *required* for dealing with non-disk devices. If I want to read a tape generated from an SGI, for example, the records may be 1MB in size. Almost all of our PCI SCSI controllers can perform such a large I/O, but DFLTPHYS prevents you from servicing such an I/O. On devices like tape, you can't break up the I/O to the device into chunks smaller than the block size. We *need* a way to perform I/Os that span more than one buffer so we can avoid the DFLTPHYS limit. -- Justin 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?200102032103.f13L3nO55354>