From: Jens Axboe <axboe@suse.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marvin Justice <mjustice@austin.rr.com>, linux-kernel@vger.kernel.org
Subject: Re: highmem question
Date: Sat, 8 Dec 2001 03:02:36 +0100 [thread overview]
Message-ID: <20011208020236.GD32569@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.30.0112071404280.29154-100000@mustard.heime.net> <01120719300102.00764@bozo> <3C116CC6.2030808@zytor.com> <01120719534703.00764@bozo> <20011208015446.GC32569@suse.de> <3C1173B8.7030905@zytor.com>
In-Reply-To: <3C1173B8.7030905@zytor.com>
On Fri, Dec 07 2001, H. Peter Anvin wrote:
> Jens Axboe wrote:
>
> > On Fri, Dec 07 2001, Marvin Justice wrote:
> >
> >>>There is no way of fixing it.
> >>>
> >>All I know is that a streaming io app I was playing with showed a drastic
> >>performance hit when the kernel was compiled with CONFIG_HIGHMEM. On W2K we
> >>saw no slowdown with 2 or even 4GB of RAM so I think solutions must exist.
> >>
> >
> > That's because of highmem page bouncing when doing I/O. There is indeed
> > a solution for this -- 2.5 or 2.4 + block-highmem-all patches will
> > happily do I/O directly to any page in your system as long as your
> > hardware supports it. I'm sure we're beating w2k with that enabled :-)
> >
>
>
> I didn't realize we were doing page bouncing for I/O in the 1-4 GB range.
> Yes, this would be an issue.
All due to the "old" block stuff requiring a virtual mapping
traditionally for doing I/O. Ugh. So yes, we are bouncing _any_ highmem
page.
--
Jens Axboe
next prev parent reply other threads:[~2001-12-08 2:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-07 13:06 highmem question Roy Sigurd Karlsbakk
2001-12-08 0:01 ` H. Peter Anvin
2001-12-08 1:30 ` Marvin Justice
2001-12-08 1:28 ` H. Peter Anvin
2001-12-08 1:53 ` Marvin Justice
2001-12-08 1:52 ` H. Peter Anvin
2001-12-08 1:54 ` Jens Axboe
2001-12-08 1:58 ` H. Peter Anvin
2001-12-08 2:02 ` Jens Axboe [this message]
2001-12-08 2:10 ` Marvin Justice
2001-12-08 2:08 ` H. Peter Anvin
2001-12-08 2:10 ` Jens Axboe
2001-12-08 3:43 ` war
2001-12-08 3:46 ` H. Peter Anvin
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