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Re: [Xen-devel] freemem-slack and large memory environments

On Thursday, February 26, 2015 01:45:16 PM Mike Latimer wrote:
> On Thursday, February 26, 2015 05:53:06 PM Stefano Stabellini wrote:
> > What is the return value of libxl_set_memory_target and
> > libxl_wait_for_free_memory in that case? Isn't it just a matter of
> > properly handle the return values?
> The return from libxl_set_memory_target is 0, as the assignment works just
> fine. I don't have the return from libxl_wait_for_free_memory in my notes,
> so I'll spin up another test and track that down.

I slightly misspoke here... In my testing, the returns are actually:

   libxl_set_memory_target = 1
   libxl_wait_for_free_memory = -5
   libxl_wait_for_memory_target = 0
      Note - libxl_wait_for_memory_target is confusing, as rc can be set
      to ERROR_FAIL, but the function returns 0 anyway (unless an error
      is encountered earlier.) I guess this just means we need to continue
      to wait...

I was testing spinning up a 64GB guest on a 2TB host. After the ballooning had 
completed, dom0 had ballooned down an extra ~320GB. On this particular 
machine, each iteration of the loop was showing only 5-7GB of memory being 
freed at a time. (The loop took 12 iterations.)


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