[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O |
Date: |
Mon, 3 Dec 2007 15:39:48 +0000 |
User-agent: |
KMail/1.9.7 |
On Monday 03 December 2007, Markus Hitter wrote:
> Am 03.12.2007 um 11:30 schrieb Laurent Vivier:
> > But if you think I should remove the buffered case, I can.
>
> In doubt, less code is always better. For the unlikely case you broke
> something badly, there's always the option to take back the patch.
>
> > BTW, do you think I should enable "cache=off" by default ?
>
> This would be fine for a transition phase, but likely, the cache=on
> case gets forgotten to be removed later. So, do it now.
I think host caching is still useful enough to be enabled by default, and
provides a significant performance increase in several cases.
- The guest typically has a relatively small quantity of RAM, compared to a
modern machine. Allowing the host OS to act as a demand-based L2 cache
allows this to be used without having to dedicate excessive quantities of ram
to qemu.
- I've seen reports that it significantly speeds up the windows installer.
- Host cache is persistent between multiple qemu runs. f you're doing anything
that requires frequent guest reboots (e.g. kernel debugging) this is going to
be a huge win.
- You're running a host OS that has limited or no caching (e.g. DOS).
I'd hope that the host OS would have cache use heuristics that would help
limit cache pollution.
Paul
- [Qemu-devel] [PATCH 0/2 v2] Open disk images with O_DIRECT, Laurent Vivier, 2007/12/03
- [Qemu-devel] [PATCH 1/2 v2] Add "cache" parameter to "-drive", Laurent Vivier, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Anthony Liguori, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Samuel Thibault, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Paul Brook, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Jamie Lokier, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Anthony Liguori, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Jamie Lokier, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Anthony Liguori, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Laurent Vivier, 2007/12/03
- Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O, Paul Brook, 2007/12/03