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

From: Li, Liang Z
Subject: Re: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization
Date: Wed, 9 Mar 2016 06:18:00 +0000

> 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?  


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