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Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk |
Date: |
Sat, 29 Jul 2006 17:31:36 +0100 |
User-agent: |
KMail/1.9.3 |
> Easy to do with the fsync infrastructure, but probably not worth
> doing since people are working on the AIO I/O backend, which would
> allow multiple outstanding writes from a guest. That, in turn,
> means I/O completion in the guest can be done when the data really
> hits disk, but without a performance impact.
Not entirely true. That only works if you allow multiple guest IO requests in
parallel, ie. some form of tagged command queueing. This requires either
improving the SCSI emulation, or implementing SATA emulation. AFAIK parallel
IDE doesn't support command queueing.
My impression what that the initial AIO implementation is just straight serial
async operation. IO wouldn't actually go any faster, it just means the guest
can do something else while it's waiting.
Paul
- [Qemu-devel] Re: [RFC][PATCH] make sure disk writes actually hit disk, (continued)
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Fabrice Bellard, 2006/07/29
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Bill C. Riemers, 2006/07/29
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jamie Lokier, 2006/07/30
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jamie Lokier, 2006/07/30
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, andrzej zaborowski, 2006/07/31
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jens Axboe, 2006/07/31
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, andrzej zaborowski, 2006/07/31
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jens Axboe, 2006/07/31
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jonas Maebe, 2006/07/31
Re: [Qemu-devel] [RFC][PATCH] make sure disk writes actually hit disk, Jens Axboe, 2006/07/31