Re: [PATCH v2 4/6] util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE

[David Hildenbrand <david@redhat.com>]

On 27.07.21 21:04, Dr. David Alan Gilbert wrote:
> * David Hildenbrand (david@redhat.com) wrote:
>> Let's simplify the case when we only want a single thread and don't have
>> to mess with signal handlers.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>   util/oslib-posix.c | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
>> index a1d309d495..1483e985c6 100644
>> --- a/util/oslib-posix.c
>> +++ b/util/oslib-posix.c
>> @@ -568,6 +568,14 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
>>       }
>>   
>>       if (use_madv_populate_write) {
>> +        /* Avoid creating a single thread for MADV_POPULATE_WRITE */
>> +        if (context.num_threads == 1) {
>> +            if (qemu_madvise(area, hpagesize * numpages,
>> +                             QEMU_MADV_POPULATE_WRITE)) {
> 
> Do you never have to fall back if this particular memory region is the
> one that can't do madv?

We sense upfront, when detecting use_madv_populate_write, whether it's 
supported on this very memory type. So, no need to fallback here.

> 
> Dave

-- 
Thanks,

David / dhildenb