From: Robert Love <rml@novell.com>
To: Bill Davidsen <davidsen@tmr.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: mmap vs. O_DIRECT
Date: Thu, 11 Nov 2004 12:13:39 -0500 [thread overview]
Message-ID: <1100193219.5358.25.camel@localhost> (raw)
In-Reply-To: <1100187716.5358.5.camel@localhost>
On Thu, 2004-11-11 at 10:41 -0500, Robert Love wrote:
> There is a difference between being synchronous and not going through
> the page cache, although in Linux we don't really have the distinction.
Rereading this, I should clarify. We definitely have the distinction.
In the case of direct I/O, you get synchronousness, no page caching, and
no use of buffers. In my statement, I meant that you cannot separate
the "no page cache" from the "synchronousness" attribute.
But you can get synchronous I/O and still get the page cache, ala
O_SYNC.
The closest you can come to normal I/O without the page cache is by
doing posix_fadvise() to prune your cache pages after you touch them.
That is definitely not what you want.
Robert Love
next prev parent reply other threads:[~2004-11-11 17:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-10 0:05 mmap vs. O_DIRECT Bill Davidsen
2004-11-10 21:13 ` Robert Love
2004-11-11 14:50 ` Bill Davidsen
2004-11-11 15:41 ` Robert Love
2004-11-11 17:13 ` Robert Love [this message]
2004-11-11 17:19 ` Avi Kivity
2004-11-11 17:22 ` Robert Love
2004-11-10 22:19 ` Alan Cox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1100193219.5358.25.camel@localhost \
--to=rml@novell.com \
--cc=davidsen@tmr.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.