On 08/03/2010 09:53 AM, Richard W.M. Jones wrote:
On Tue, Aug 03, 2010 at 05:38:25PM +0300, Avi Kivity wrote:
The time will only continue to grow as you add features and as the
distro bloats naturally.
Much better to create it once and only update it if some dependent
file changes (basically the current on-the-fly code + save a list of
file timestamps).
This applies to both cases, the initrd could also be saved, so:
Total saving: 115ms.
815 ms by my arithmetic.
no, not true, 115ms.
You also save 3*N-2*P memory where N is the size of your initrd and
P is the actual amount used by the guest.
Can you explain this?
Loading a file into memory is plenty fast if you use the standard
interfaces. -kernel -initrd is a specialized interface.
Why bother with any command line options at all? After all, they keep
changing and causing problems for qemu's users ... Apparently we're
all doing stuff "wrong", in ways that are never explained by the
developers.
Let's be fair. I think we've all agreed to adjust the fw_cfg interface
to implement DMA. The only requirement was that the DMA operation not
be triggered from a single port I/O but rather based on a polling
operation which better fits the way real hardware works.
Is this a regression? Probably. But performance regressions that
result from correctness fixes don't get reverted. We have to find an
approach to improve performance without impacting correctness.
That said, the general view of -kernel/-append is that these are
developer options and we don't really look at it as a performance
critical interface. We could do a better job of communicating this to
users but that's true of most of the features we support.
Regards,
Anthony Liguori
Rich.
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