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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT) |
Date: | Wed, 21 May 2008 12:53:52 -0500 |
User-agent: | Thunderbird 2.0.0.14 (X11/20080501) |
Andrea Arcangeli wrote:
On Wed, May 21, 2008 at 08:18:01PM +0300, Avi Kivity wrote:Yes, that's the reason. Here zerocopy is not the motivation; instead, we have host-cached pages that are used directly in the guest. So we get both reduced memory footprint, and host caching. O_DIRECT reduces the memory footprint but kills host caching.Sure. So MAP_SHARED+remap_file_pages should work just fine to achieve zerocopy I/O.
MAP_SHARED cannot be done transparently to the guest, that's the motivating reason behind MAP_PRIVATE.
Regards, Anthony Liguori
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