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From: Jitendra Kolhe <jitendra.kolhe@hpe.com>
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Date: Thu, 23 Feb 2017 16:27:18 +0530
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Subject: Re: [Qemu-devel] [PATCH v3] mem-prealloc: reduce large guest
 start-up and migration time.
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: ehabkost@redhat.com, imammedo@redhat.com, crosthwaite.peter@gmail.com, eblake@redhat.com, armbru@redhat.com, peter.maydell@linaro.org, kwolf@redhat.com, pl@kamp.de, sw@weilnetz.de, quintela@redhat.com, dgilbert@redhat.com, berrange@redhat.com, renganathan.meenakshisundaram@hpe.com, mohan_parthasarathy@hpe.com

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");
>>      }