Hi Andrey,
Thanks for your reply!
You may try do play with SCHED_RT, I have found it hard to use for
myself, but you can achieve your goal by adding small RT slices via
``cpu'' cgroup to vcpu/emulator threads, it dramatically increases
overall VM` responsibility.
I'm not quite sure I understand your suggestion.
Do you mean that you set the process priority to real-time on each
qemu-kvm process, and then use cgroups cpu.rt_runtime_us /
cpu.rt_period_us to restrict the amount of CPU time those processes can
receive?
I'm not sure how that would apply here, as I have only one qemu-kvm
process and it is not non-responsive because of the lack of allocated
CPU time slices - but rather because some I/Os take a long time to
complete, and other I/Os apparently have to wait for those to complete.
threads. Of course, some Ceph tuning like writeback cache and large
journal may help you too, I`m speaking primarily of VM` performance by
I have been considering the journal as something where I could improve
performance by tweaking the setup. I have set aside 10 GB of space for
the journal, but I'm not sure if this is too little - or if the size
really doesn't matter that much when it is on the same mdraid as the
data itself.
Is there a tool that can tell me how much of my journal space that is
actually actively being used?
I.e. I'm looking for something that could tell me, if increasing the
size of the journal or placing it on a seperate (SSD) disk could solve
my problem.
How do I change the size of the writeback cache when using qemu-kvm like
I do?
Does setting rbd cache size in ceph.conf have any effect on qemu-kvm,
where the drive is defined as:
format=rbd,file=rbd:data/image1:rbd_cache=1,if=virtio
--
Jens Kristian Søgaard, Mermaid Consulting ApS,
jens@xxxxxxxxxxxxxxxxxxxx,
http://www.mermaidconsulting.com/
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