On 09/27/2017 04:55 PM, Blair Bethwaite wrote:
Hi Prema
On 28 September 2017 at 07:10, Premysl Kouril <premysl.kou...@gmail.com> wrote:
Hi, I work with Jakub (the op of this thread) and here is my two
cents: I think what is critical to realize is that KVM virtual
machines can have substantial memory overhead of up to 25% of memory,
allocated to KVM virtual machine itself. This overhead memory is not
I'm curious what sort of VM configuration causes such high overheads,
is this when using highly tuned virt devices with very large buffers?
For what it's worth we ran into issues a couple years back with I/O to
RDB-backed disks in writethrough/writeback. There was a bug that allowed a very
large number of in-flight operations if the ceph server couldn't keep up with
the aggregate load. We hacked a local solution, I'm not sure if it's been dealt
with upstream.
I think virtio networking has also caused issues, though not as bad. (But
noticeable when running close to the line.)
Chris
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