From: "H. Peter Anvin" <hpa@zytor.com>
To: Jens Axboe <axboe@suse.de>
Cc: Marvin Justice <mjustice@austin.rr.com>, linux-kernel@vger.kernel.org
Subject: Re: highmem question
Date: Fri, 07 Dec 2001 17:58:16 -0800 [thread overview]
Message-ID: <3C1173B8.7030905@zytor.com> (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>
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.
-hpa
next prev parent reply other threads:[~2001-12-08 1:58 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 [this message]
2001-12-08 2:02 ` Jens Axboe
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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