From: Andrea Arcangeli <andrea@qumranet.com>
To: Avi Kivity <avi@qumranet.com>
Cc: Blue Swirl <blauwirbel@gmail.com>,
Laurent Vivier <Laurent.Vivier@bull.net>,
qemu-devel@nongnu.org, Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT)
Date: Wed, 21 May 2008 19:01:29 +0200 [thread overview]
Message-ID: <20080521170129.GF22488@duo.random> (raw)
In-Reply-To: <48345258.9040004@qumranet.com>
On Wed, May 21, 2008 at 07:48:24PM +0300, Avi Kivity wrote:
> Hmm, if remap_file_pages() supports MAP_PRIVATE, that solves all the
> problems neatly.
>
> Andrea, do you know if that combination works?
No, it only supports MAP_SHARED. Why would anyone want MAP_PRIVATE for
real I/O operations? MAP_PRIVATE is primarily for binaries and things
that are readonly on disk and that we may want to update (like for
dynamic linking w/o hardlinking).
Or is that for -snapshot support, to keep the modifications in
anonymous ram?
I imagine you want remap_file_pages for zerocopy I/O without using
O_DIRECT. If you use O_DIRECT you don't need mmap. However O_DIRECT
work best with kernel asyncio for small seeking blocks so all I/O can
be submitted at the same time. writev also works better than write for
O_DIRECT.
next prev parent reply other threads:[~2008-05-21 17:29 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-20 11:32 [Qemu-devel] [PATCH][v2] Align file accesses with cache=off (O_DIRECT) Laurent Vivier
2008-05-20 19:47 ` [Qemu-devel] " Anthony Liguori
2008-05-20 22:36 ` Jamie Lokier
2008-05-20 22:52 ` Paul Brook
2008-05-20 22:59 ` Laurent Vivier
2008-05-21 0:54 ` Paul Brook
2008-05-21 7:59 ` Laurent Vivier
2008-05-21 0:58 ` Anthony Liguori
2008-05-21 1:04 ` Jamie Lokier
2008-05-21 1:05 ` Anthony Liguori
2008-05-21 8:06 ` Kevin Wolf
2008-05-21 1:05 ` Paul Brook
2008-05-21 1:14 ` Anthony Liguori
2008-05-21 8:24 ` Kevin Wolf
2008-05-21 12:26 ` Jamie Lokier
2008-05-21 12:37 ` Avi Kivity
2008-05-21 13:41 ` Jamie Lokier
2008-05-21 13:55 ` Anthony Liguori
2008-05-21 14:17 ` Avi Kivity
2008-05-21 14:26 ` Anthony Liguori
2008-05-21 14:57 ` Avi Kivity
2008-05-21 15:34 ` Jamie Lokier
2008-05-21 16:02 ` Anthony Liguori
2008-05-21 16:24 ` Jamie Lokier
2008-05-21 16:48 ` Avi Kivity
2008-05-21 17:01 ` Andrea Arcangeli [this message]
2008-05-21 17:18 ` Avi Kivity
2008-05-21 17:47 ` Andrea Arcangeli
2008-05-21 17:53 ` Anthony Liguori
2008-05-21 18:08 ` Andrea Arcangeli
2008-05-21 18:25 ` Anthony Liguori
2008-05-21 20:13 ` Andrea Arcangeli
2008-05-21 20:35 ` Anthony Liguori
2008-05-21 20:42 ` Andrea Arcangeli
2008-05-21 18:29 ` Avi Kivity
2008-05-21 16:45 ` Avi Kivity
2008-05-21 16:44 ` Avi Kivity
2008-05-20 23:04 ` Laurent Vivier
2008-05-20 23:13 ` Jamie Lokier
2008-05-21 1:00 ` Anthony Liguori
2008-05-21 1:19 ` Jamie Lokier
2008-05-21 2:12 ` Anthony Liguori
2008-05-21 8:27 ` Andreas Färber
2008-05-21 14:06 ` Anthony Liguori
2008-05-21 15:31 ` Jamie Lokier
2008-05-21 11:43 ` Jamie Lokier
2008-05-23 9:12 ` Laurent Vivier
2008-05-28 7:01 ` Kevin Wolf
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