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Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_D
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT) |
Date: |
Wed, 21 May 2008 16:34:54 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Avi Kivity wrote:
> Here's a summary of the use cases I saw so far:
>
> - casual use, no critical data: write back cache
>
> - backing file shared among many guests: read-only, cached
>
> - desktop system, but don't lose my data: O_SYNC
> (significant resources on the host)
>
> - dedicated virtualization engine: O_DIRECT
> (most host resources assigned to guests)
Sounds alright, but on _my_ desktop system (a laptop), I would use O_DIRECT.
There isn't enough RAM in my system to be happy duplicating data in
guests and hosts at the same time. VMs are quite demanding on RAM.
However, if you find a way to map host cached pages into the guest
without copying - so sharing the RAM - that would be excellent. It
can be done in principle, by remapping pages to satisfy IDE/SCSI DMA
requests. I don't know if it would be fast enough. Perhaps it would
work better in KVM than QEMU.
-- Jamie
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), (continued)
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Paul Brook, 2008/05/20
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/20
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Kevin Wolf, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Jamie Lokier, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Avi Kivity, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Jamie Lokier, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Avi Kivity, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Avi Kivity, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT),
Jamie Lokier <=
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Jamie Lokier, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Avi Kivity, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Andrea Arcangeli, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Avi Kivity, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Andrea Arcangeli, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Andrea Arcangeli, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Anthony Liguori, 2008/05/21
- Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off (O_DIRECT), Andrea Arcangeli, 2008/05/21