On Thu, Aug 18, 2022 at 2:46 PM Milan Zamazal <mzama...@redhat.com> wrote:
> Fangge Jin <f...@redhat.com> writes: > > > I can share some test results with you: > > 1. If no memtune->hard_limit is set when start a vm, the default memlock > > hard limit is 64MB > > 2. If memtune->hard_limit is set when start a vm, memlock hard limit will > > be set to the value of memtune->hard_limit > > 3. If memtune->hard_limit is updated at run-time, memlock hard limit > won't > > be changed accordingly > > > > And some additional knowledge: > > 1. memlock hard limit can be shown by ‘prlimit -p <pid-of-qemu> -l’ > > 2. The default value of memlock hard limit can be changed by setting > > LimitMEMLOCK in /usr/lib/systemd/system/virtqemud.service > > Ah, that explains it to me, thank you. And since in the default case > the systemd limit is not reported in <memtune> of a running VM, I assume > libvirt takes it as "not set" and sets the higher limit when setting up > a zero-copy migration. Good. > Not sure whether you already know this, but I had a hard time differentiating the two concepts: 1. memlock hard limit(shown by prlimit): the hard limit for locked host memory 2. memtune hard limit(memtune->hard_limit): the hard limit for in-use host memory, this memory can be swapped out. > > Regards, > Milan >
