Hi,
> The other problem to consider is the possibility of deadlock under memory
> pressure. This is a problem with any network file system or block device
> that is backed by a user-level process on the same host. When the VM
> system is under memory pressure, it will ask the fs to write out some
> dirty pages, which will be sent to a user-level process, that may need to
> allocate memory, which will block until the kernel is able to free more
> memory. Deadlock.
>
> Machines with lots of memory and very conservative VM settings can
> probably avoid this in practice, but it is technically possible,
> and with default settings isn't terribly hard to trigger.
Am I correct to assume that this problem can't be triggered if :
- Kernel RBD is running on the physical machine host ( dom0 on Xen )
- OSD process runs in a VM inside a DomU ( and has it's own dedicated
physical memory which isn't even 'seen' by the Dom0, only the
hypervisor can see it).
Cheers,
Sylvain
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