[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive
From: |
Christoph Hellwig |
Subject: |
Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive |
Date: |
Mon, 17 May 2010 14:40:18 +0200 |
User-agent: |
Mutt/1.3.28i |
On Tue, May 11, 2010 at 11:11:12PM +0100, Paul Brook wrote:
> .. though it may be a kernel bug rather that a qemu bug, depending on the
> exact details. Either way, I consider any mode that inhibits host filesystem
> write cache but not volatile drive cache to be pretty worthless. Either we
> guaranteed data integrity on completion or we don't.
O_DIRECT just means bypassing the pagecache, it does not mean flushing
the disk cache on every access, which for certain workloads can be very
painful. It also doesn't require a synchronous writeout of metadata
required to reach the data, e.g. in case when we have to allocate blocks
for a sparse image file.
To get the behaviour you want you need O_DIRECT|O_DSYNC, which is
something that is not exposed by qemu's current cache= suboption.
If we want to implement this properly we need to split the cache option,
as I already mentioned. This would also have benefits in other areas,
but again refer to my previous mail for that.
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, (continued)
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Paul Brook, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Avi Kivity, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Jamie Lokier, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Anthony Liguori, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Jamie Lokier, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Alexander Graf, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Jamie Lokier, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Paul Brook, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Paul Brook, 2010/05/11
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Jamie Lokier, 2010/05/12
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive,
Christoph Hellwig <=
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Markus Armbruster, 2010/05/14
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Christoph Hellwig, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Alexander Graf, 2010/05/17
- Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Avi Kivity, 2010/05/11
- [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Alexander Graf, 2010/05/12
- [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Kevin Wolf, 2010/05/12
- [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive, Alexander Graf, 2010/05/12
Re: [Qemu-devel] [PATCH 1/2] Add no-op aio emulation stub, Stefan Hajnoczi, 2010/05/11
[Qemu-devel] Re: [PATCH 1/2] Add no-op aio emulation stub, Kevin Wolf, 2010/05/11
Re: [Qemu-devel] [PATCH 0/2] Enable qemu block layer to not flush, Anthony Liguori, 2010/05/10