RE: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization

From: Li, Liang Z
Date: Wed Mar 09 2016 - 01:18:19 EST

> On 04/03/2016 15:26, Li, Liang Z wrote:
> >> >
> >> > The memory usage will keep increasing due to ever growing caches,
> >> > etc, so you'll be left with very little free memory fairly soon.
> >> >
> > I don't think so.
> >
> Roman is right. For example, here I am looking at a 64 GB (physical) machine
> which was booted about 30 minutes ago, and which is running disk-heavy
> workloads (installing VMs).
> Since I have started writing this email (2 minutes?), the amount of free
> memory has already gone down from 37 GB to 33 GB. I expect that by the
> time I have finished running the workload, in two hours, it will not have any
> free memory.
> Paolo

I have a VM which has 2GB of RAM, when the guest booted, there were about 1.4GB of free pages.
Then I tried to download a large file from the internet with the browser, after the downloading finished,
there were only 72MB of free pages left, as Roman pointed out, there were quite a lot of Cached memory.
Then I tried to compile the QEMU, after the compiling finished, there were about 1.3G free pages.

So even the cache will increase to a large amount, it will be freed if there are some other specific workloads.
The cache memory is a big issue that should be taken into consideration.
How about reclaim some cache before getting the free pages information?