On 12/19/23 9:01 PM, Matthew Wilcox wrote:
> On Tue, Dec 19, 2023 at 01:58:21PM +0800, Jingbo Xu wrote:
>> On 12/19/23 12:06 PM, Matthew Wilcox wrote:
>>> On Tue, Dec 19, 2023 at 10:42:46AM +0800, Jingbo Xu wrote:
>>>> } else {
>>>> bdi->max_ratio = max_ratio;
>>>> - bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
>>>> + bdi->max_prop_frac = div64_u64(FPROP_FRAC_BASE * max_ratio,
>>>> + 100 * BDI_RATIO_SCALE);
>>>> }
>>>
>>> Why use div64_u64 here?
>>>
>>> FPROP_FRAC_BASE is an unsigned long. max_ratio is an unsigned int, so
>>> the numerator is an unsigned long. BDI_RATIO_SCALE is 10,000, so the
>>> numerator is an unsigned int. There's no 64-bit arithmetic needed here.
>>
>> Yes, div64_u64() is actually not needed here. So it seems
>>
>> bdi->max_prop_frac = FPROP_FRAC_BASE * max_ratio / 100 / BDI_RATIO_SCALE;
>>
>> is adequate?
>
> I'd rather spell that as:
>
> bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) /
> (100 * BDI_RATIO_SCALE);
>
> It's closer to how you'd write it out mathematically and so it reads
> more easily. At least for me.
Thanks, I would send v3 soon.
--
Thanks,
Jingbo
