[OmniOS-discuss] qemu-system-x86_64 can not locked enough memory

[Fucai Liang （BLCT）]

Thank for  your help!

when the server boot up, it has 7989066 pages  availrmem.  after I launch one VM (8Gmemory),  availrmem decrease to 4756624 .



7989066-4756624 = 3232442

3232442/256 = 12626.7265625 / 1024 = 12.3G



root at BLCC01:/root# mdb -ke 'availrmem/D ; pages_pp_maximum/D'
availrmem:
availrmem:      7989066
pages_pp_maximum:
pages_pp_maximum:               325044

root at BLCC01:/root# qemu-system-x86_64 -enable-kvm -vnc 0.0.0.0:12 -cpu host -smp 4 -m 8192 -no-hpe



root at BLCC01:/root# mdb -ke 'availrmem/D ; pages_pp_maximum/D'
availrmem:
availrmem:      4756624
pages_pp_maximum:
pages_pp_maximum:               325044
root at BLCC01:/root#


That mean the VM  use 12.3G availrmem , how it happens ?

Thank !




------------------------------
fcliang




On Dec 2, 2015, at 1:37, Joshua M. Clulow <josh at sysmgr.org> wrote:

> On 1 December 2015 at 09:11, Dan McDonald <danmcd at omniti.com> wrote:
>>> On Dec 1, 2015, at 12:03 PM, Fucai.Liang <fcliang at baolict.com> wrote:
>>> then I start the third vm (4G memory), it got the following error :
>>> qemu-system-x86_64 -enable-kvm -vnc 0.0.0.0:2 -cpu host -smp 2 -m 4096 -no-hpet
>>> 
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying...
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying...
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying...
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying...
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying...
>>> qemu_mlock: have only locked 1940582400 of 4294967296 bytes; still trying…
>>> 
>>> I got 15G free memory in the system, why qemu-system-x86_64 can not locked enough memory ？
>> What does "vmstat 1 5" say prior to your launch of the third VM?
> 
> I suspect it will show you have free memory available, but that what
> is really happening is getting here:
> 
>  https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/vm/seg_vn.c#L7989-L8002
> 
> This is likely failing in page_pp_lock() because "availrmem" has
> fallen below "pages_pp_maximum":
> 
>  https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/vm/vm_page.c#L3817-L3818
> 
> We set this value here, though it can be overridden in "/etc/system":
> 
>  https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/vm/vm_page.c#L423-L436
> 
> You can look at the current values with mdb:
> 
>  mdb -ke 'availrmem/D ; pages_pp_maximum/D'
> 
> Increasing this value doesn't seem to be without risk: I believe that
> it can lead to memory exhaustion deadlocks, amongst other things.  I
> don't know if it's expected to be tuneable without a reboot.
> 
> 
> Cheers.
> 
> -- 
> Joshua M. Clulow
> UNIX Admin/Developer
> http://blog.sysmgr.org

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