On 03/15/2010 08:48 PM, Anthony Liguori wrote:
On 03/15/2010 04:27 AM, Avi Kivity wrote:
That's only beneficial if the cache is shared. Otherwise, you could
use the balloon to evict cache when memory is tight.
Shared cache is mostly a desktop thing where users run similar
workloads. For servers, it's much less likely. So a modified-guest
doesn't help a lot here.
Not really. In many cloud environments, there's a set of common
images that are instantiated on each node. Usually this is because
you're running a horizontally scalable application or because you're
supporting an ephemeral storage model.
But will these servers actually benefit from shared cache? So the
images are shared, they boot up, what then?
- apache really won't like serving static files from the host pagecache
- dynamic content (java, cgi) will be mostly in anonymous memory, not
pagecache
- ditto for application servers
- what else are people doing?
In fact, with ephemeral storage, you typically want to use
cache=writeback since you aren't providing data guarantees across
shutdown/failure.
Interesting point.
We'd need a cache=volatile for this use case to avoid the fdatasync()s
we do now. Also useful for -snapshot. In fact I have a patch for this
somewhere I can dig out.
--
error compiling committee.c: too many arguments to function
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