Re: [Qemu-devel] problems with 1G hugepages and linux 3.12-rc3

[Gleb Natapov]

Copying Andrea,

On Sun, Oct 06, 2013 at 02:47:41AM +0200, andy123 wrote:
> Hi,
> 
> as the subject states, I have some problems with 1G hugepages with 
> qemu(-vfio-git) on Linux 3.12-rc3.
> 
> I start qemu like this, for example:
> "/usr/bin/qemu-system-x86_64 -enable-kvm -m 1024 -mem-path /dev/hugepages 
> -drive file=/files/vm/arch.img,if=virtio,media=disk -monitor stdio"
> where /dev/hugepages is "hugetlbfs on /dev/hugepages type hugetlbfs 
> (rw,relatime,mode=1770,gid=78,pagesize=1G,pagesize=1G)"
> and the kernel is booted with "hugepagesz=1G hugepages=4".
> This result in lots of error message in dmesg, as seen here: 
> https://gist.github.com/ajs124/6842823 (starting at 18:04:28)
> 
> After starting and stopping multiple virtual machines, the hugepages seem to 
> "fill up" and qemu outputs
> "file_ram_alloc: can't mmap RAM pages: Cannot allocate memory", but works 
> anyways.
> With fill up, I mean that I can start qemu 2 time with "-m 2048" and 4 times 
> with "-m 1024", before it fails to mmap.
> 
I can reproduce huge page leak, but not oops, but they can be related.
Can you revert 11feeb498086a3a5907b8148bdf1786a9b18fc55 and retry?

> This works without any problems in 3.11.x and also with 2M hugepages (umount 
> /dev/hugepages && mount -t hugetlbfs -o pagesize=2048k /dev/hugepages).
> 
> I'm running this in arch linux and there has already been some discussion on 
> the arch forums 
> (https://bbs.archlinux.org/viewtopic.php?pid=1333469#p1333469) but I tried to 
> add everything I wrote over there in this mail.
> 
> In case I missed something or you need more information, I'll happily supply 
> it in order to get this resolved.
> 
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--
                        Gleb.