[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [RFC] support memory reserved feature and optimize mloc
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC] support memory reserved feature and optimize mlock guest memory propose |
Date: |
Thu, 06 Mar 2014 09:41:40 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
Il 06/03/2014 09:06, Zhanghailiang ha scritto:
>
>> Il 05/03/2014 09:01, Zhanghailiang ha scritto:
>>> Hi all:
>>>
>>> Currently, we use cgroup(memory) to support memory QoS on KVM
>>> platform, and use "mlock" on qemu to support "memory reserved".
>>>
>>> The "mlock" seems to be not appropriate.
>>>
>>> Now qemu "mlock" memory in the main thread, which would lock iothread
>>> (qemu_mutex_lock_iothread), if the memory size is large, that will
>>> consume lots of time.
>>>
>>> It means whenever we want to set a new 'mlock', the VM would be
>>> blocked for a while.
>>
>> I'm not sure I understand how the mlock-ed memory is used. Are you using a
>> custom malloc, for example with g_mem_set_vtable?
>>
>> Paolo
>
> Hi Paolo:
>
> Thanks for your reply.
> As you know qemu has an option "-mlock", I think it has some problems.
> If we set "-realtime mlock=on", then qemu will mlockall vm's memory, It is a
> very time consuming action, and it will block the libvirt api until it
> finished.
> so I think it is better to do 'mlock' asynchronously, the flow chart can be
> described like below.
Is an asynchronous mlock valid for all workloads? Until the mlock
finishes, there is no guarantee that the guest will have
"real-time--friendly" response to memory allocation.
> Is it ok?
> Flow chart:
> main funciton qmp command "set_ram_minguarantee"
> | |
> | |
> create "mlock" thread change value of lock_ram_size
> | |
> | |
> |------>thread wait<-------------wake up "mlock" thread
> | |
> | |
> | |
> |-------mlock(lock_ram_zie)
Also, I'm not sure what the arguments to mlock are. How do you find the
address range to pass to mlock?
Paolo