Re: [Qemu-devel] Memory: how to determine the max memory size of one VM?

[Paul Brook]

> Am 11.02.2012 00:25, schrieb Paul Brook:
> >> ii) Some tracing of mine indicates QEMU has a highly dynamic memory
> >> usage during runtime, be it due to network layer, block layer or
> >> whatever exactly.
> > 
> > We do? Significant compared to the size of guest ram?  That sounds like a
> > bug.
> 
> Attached is a gnuplot from a simpletrace trace file while installing a
> SLES 11 SP2 Release Candidate over slirp to virtio with -m 8G on an 8
> GiB host (post-1.0 master).
> 
> It's not fully scientifically correct (it doesn't take into account
> memory allocations not traced by QEMU itself, like pthreads) but it
> suggests that after the initial surge to ~8.7 GB we have a fluctuation
> of ~0.2 GB for 8 GiB guest RAM. It's larger than I'd expect at least.
> 
> Since the user was close to the limit, this lead to an abort. In their
> case it was a pthread_create() that failed, and we used tap + virtio.

Hmm, yes, we're clearly allocating some very large buffers somewhere.

Paul