Re: [Qemu-devel] [PATCH] vl: Adjust the place of calling mlockall to speedup VM's startup

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

On 2014/9/23 16:35, Hu Tao wrote:
> On Tue, Sep 23, 2014 at 11:30:26AM +0300, Michael S. Tsirkin wrote:
>> On Tue, Sep 23, 2014 at 03:57:47PM +0800, zhanghailiang wrote:
>>> If we configure mlock=on and memory policy=bind at the same time,
>>> It will consume lots of time for system to treat with memory,
>>> especially when call mbind after mlockall.
>>>
>>> Adjust the place of calling mlockall, calling mbind before mlockall
>>> can remarkably reduce the time of VM's startup.
>>>
>>> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
>>
>> The idea makes absolute sense to me:
>> bind after lock will force data copy of
>> all pages. bind before lock gives us an
>> indication where to put data on fault in.
>
> Agreed.
>
>>
>> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>>
>>
>>> ---
>>> Hi,
>>>
>>> Actually, for mbind and mlockall, i have made a test about the time consuming
>>> for the different call sequence.
>>>
>>> The results is shown below. It is obviously that mlockall called before mbind is
>>> more time-consuming.
>>>
>>> Besides, this patch is OK with memory hotplug.
>>>
>>> TEST CODE:
>>>      if (mbind_first) {
>>>          printf("mbind --> mlockall\n");
>>>          mbind(ptr, ram_size/2, MPOL_BIND, &node0mask, 2,
>>>                MPOL_MF_STRICT | MPOL_MF_MOVE);
>>>          mbind(ptr + ram_size/2, ram_size/2, MPOL_BIND, &node1mask, 2,
>>>                MPOL_MF_STRICT | MPOL_MF_MOVE);
>>>          mlockall(MCL_CURRENT | MCL_FUTURE);
>>>      } else {
>>>          printf("mlockall --> mbind\n");
>>>          mlockall(MCL_CURRENT | MCL_FUTURE);
>>>          mbind(ptr, ram_size/2, MPOL_BIND, &node0mask, 2 ,
>>>                MPOL_MF_STRICT | MPOL_MF_MOVE);
>>>          mbind(ptr + ram_size/2, ram_size/2, MPOL_BIND, &node1mask, 2,
>>>                MPOL_MF_STRICT | MPOL_MF_MOVE);
>>>      }
>>>
>>> RESULT 1:
>>> #time /home/test_mbind 10240 0
>>> memroy size 10737418240
>>> mlockall --> mbind
>>>
>>> real    0m11.886s
>>> user    0m0.004s
>>> sys     0m11.865s
>>> #time /home/test_mbind 10240 1
>>> memroy size 10737418240
>>> mbind --> mlockall
>>>
>>> real    0m5.334s
>>> user    0m0.000s
>>> sys     0m5.324s
>>>
>>> RESULT 2:
>>> #time /home/test_mbind 4096 0
>>> memroy size 4294967296
>>> mlockall --> mbind
>>>
>>> real    0m5.503s
>>> user    0m0.000s
>>> sys     0m5.492s
>>> #time /home/test_mbind 4096 1
>>> memroy size 4294967296
>>> mbind --> mlockall
>>>
>>> real    0m2.139s
>>> user    0m0.000s
>>> sys     0m2.132s
>>>
>>> Best Regards,
>>> zhanghailiang
>>> ---
>>>   vl.c | 11 +++++------
>>>   1 file changed, 5 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/vl.c b/vl.c
>>> index dc792fe..adf4770 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -134,6 +134,7 @@ const char* keyboard_layout = NULL;
>>>   ram_addr_t ram_size;
>>>   const char *mem_path = NULL;
>>>   int mem_prealloc = 0; /* force preallocation of physical target memory */
>>> +int enable_mlock = false;
>
> Why not bool?
>

Er, that is my fault, Will fix it and submit V2, Thanks;)

> Regards,
> Hu
>
> .
>