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 16:30, 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.
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>
>

Thanks for your quick reviewing..

Best Regards,
zhanghailiang

>> ---
>> 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;
>>   int nb_nics;
>>   NICInfo nd_table[MAX_NICS];
>>   int autostart;
>> @@ -1421,12 +1422,8 @@ static void smp_parse(QemuOpts *opts)
>>
>>   }
>>
>> -static void configure_realtime(QemuOpts *opts)
>> +static void realtime_init(void)
>>   {
>> -    bool enable_mlock;
>> -
>> -    enable_mlock = qemu_opt_get_bool(opts, "mlock", true);
>> -
>>       if (enable_mlock) {
>>           if (os_mlock() < 0) {
>>               fprintf(stderr, "qemu: locking memory failed\n");
>> @@ -3973,7 +3970,7 @@ int main(int argc, char **argv, char **envp)
>>                   if (!opts) {
>>                       exit(1);
>>                   }
>> -                configure_realtime(opts);
>> +                enable_mlock = qemu_opt_get_bool(opts, "mlock", true);
>>                   break;
>>               case QEMU_OPTION_msg:
>>                   opts = qemu_opts_parse(qemu_find_opts("msg"), optarg, 0);
>> @@ -4441,6 +4438,8 @@ int main(int argc, char **argv, char **envp)
>>
>>       machine_class->init(current_machine);
>>
>> +    realtime_init();
>> +
>>       audio_init();
>>
>>       cpu_synchronize_all_post_init();
>> --
>> 1.7.12.4
>>
>
> .
>