Re: [Qemu-devel] [PATCH] qemu-timer: remove unnecessary code

[Cao jin <caoj.fnst@cn.fujitsu.com>]

On 07/13/2016 06:21 PM, Paolo Bonzini wrote:
>
>
> On 13/07/2016 11:06, Cao jin wrote:
>> When passed argument 'ns' is 0, macro DIV_ROUND_UP will return 0 also.
>
> It's potentially slower though.
>

Is it because the function in the i/o loop path, so the potentially 
extra arithmetical instructions matters?

> Paolo
>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
>> ---
>>   qemu-timer.c | 6 +-----
>>   1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/qemu-timer.c b/qemu-timer.c
>> index eb22e92..cfe0893 100644
>> --- a/qemu-timer.c
>> +++ b/qemu-timer.c
>> @@ -285,12 +285,8 @@ int qemu_timeout_ns_to_ms(int64_t ns)
>>           return -1;
>>       }
>>
>> -    if (!ns) {
>> -        return 0;
>> -    }
>> -
>>       /* Always round up, because it's better to wait too long than to wait too
>> -     * little and effectively busy-wait
>> +     * short and effectively busy-wait
>>        */
>>       ms = DIV_ROUND_UP(ns, SCALE_MS);
>>
>>
>
>
>

-- 
Yours Sincerely,

Cao jin