linux-kernel - Re: Collapse all Print all In new window Guaranteed allocation of huge pages (1G) using movablecore=N doesn't seem to work at all.

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Date:   Sat, 4 Nov 2017 01:33:31 +0200
From:   Maxim Levitsky <maximlevitsky@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: Collapse all Print all In new window Guaranteed allocation of
 huge pages (1G) using movablecore=N doesn't seem to work at all.

Sorry for garbaged title - I copy & pased from older mail which I by
mistake sent in HTML (had to use gmail web interface here)

Beset regards,
         Maxim Levitsky

On Sat, Nov 4, 2017 at 1:31 AM, Maxim Levitsky <maximlevitsky@...il.com> wrote:
> Hi!
>
> My system has 64G of ram and I want to create 32 1G huge pages to use
> in KVM virtualization,
> on demand, only when VM is running.
>
> So I booted the kernel with
> 'hugepagesz=1G hugepages=0 default_hugepagesz=1G movablecore=40G'
>
> However I still can't allocate the pages reliably.
> For instance this simple script is enough to make it not possible to
> even allocate one 1G huge page after few dozens of iterations:
>
> while true ; do
>     sudo hugeadm  --enable-zone-movable  --pool-pages-min 1G:0G
>     sudo hugeadm  --enable-zone-movable  --pool-pages-min 1G:60G
> done
>
>
> I disabled mlock systemwide (now ulimit -l shows 0), I still see 8
> pages mlocked in  zone 'Movable' but this is not enough to explain
> this
> nr_mlock     8
>
> I do have around 64GB of swap too, but I see no even an attempt to use it.
>
>
> # free
>               total        used        free      shared  buff/cache   available
> Mem:       65887928     1748344    62640276       61688     1499308    62053832
> Swap:      67108860           0    67108860
>
> Any idea about what is going on?
>
> This was tested on 4.14.0-rc5 (my custom compiled) and on several
> older kernels from ubuntu repositories.
>
> Disabling/enabling transparent huge pages in the kernel config didn't
> make a difference.
>
> VT-d was enabled during the tests (intel_iommu=on,igfx_off) is that
> would make any difference, but no VM was started when I run the above
> script, in fact I run it just after the system booted.
>
> Best regards,
>           Maxim Levitsky