Re: [Qemu-devel] [PATCH v3] mem-prealloc: reduce large guest start-up and migration time.

[Jitendra Kolhe]

On 2/23/2017 3:31 PM, Paolo Bonzini wrote:
> 
> 
> On 23/02/2017 10:56, Jitendra Kolhe wrote:
>>      if (sigsetjmp(sigjump, 1)) {
>> -        error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
>> -            "pages available to allocate guest RAM\n");
>> +        memset_thread_failed = true;
> 
> This sigsetjmp is not needed, no one can siglongjmp to it.
> 
> The SIG_UNBLOCK/SIG_BLOCK in the main thread is not necessary, either.
> 
>>      } else {
>> -        int i;
>>          size_t hpagesize = qemu_fd_getpagesize(fd);
>>          size_t numpages = DIV_ROUND_UP(memory, hpagesize);
>>  
>> -        /* MAP_POPULATE silently ignores failures */
>> -        for (i = 0; i < numpages; i++) {
>> -            memset(area + (hpagesize * i), 0, 1);
>> -        }
>> +        /* touch pages simultaneously */
>> +        touch_all_pages(area, hpagesize, numpages, smp_cpus);
> 
> ... and now touch_all_pages can just return memset_thread_failed, which
> simplifies the code a bit.
> 

sure, will make change accordingly.

- Jitendra

> Paolo
> 
>> +    }
>> +    if (memset_thread_failed) {
>> +        error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
>> +            "pages available to allocate guest RAM");
>>      }