2017-11-28 11:11 GMT+08:00 Yafang Shao <laoar.shao@xxxxxxxxx>:
> Hi Michal,
>
> What about bellow change ?
> It makes the function domain_dirty_limits() more clear.
> And the result will have a higher precision.
>
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 8a15511..2b5e507 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -397,8 +397,8 @@ static void domain_dirty_limits(struct
> dirty_throttle_control *dtc)
> unsigned long bytes = vm_dirty_bytes;
> unsigned long bg_bytes = dirty_background_bytes;
> /* convert ratios to per-PAGE_SIZE for higher precision */
> - unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100;
> - unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100;
> + unsigned long ratio = vm_dirty_ratio;
> + unsigned long bg_ratio = dirty_background_ratio;
> unsigned long thresh;
> unsigned long bg_thresh;
> struct task_struct *tsk;
> @@ -416,28 +416,33 @@ static void domain_dirty_limits(struct
> dirty_throttle_control *dtc)
> */
> if (bytes)
> ratio = min(DIV_ROUND_UP(bytes, global_avail),
> - PAGE_SIZE);
> + 100);
> if (bg_bytes)
> bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail),
> - PAGE_SIZE);
> + 99); /* bg_ratio should less than ratio */
> bytes = bg_bytes = 0;
> }
Errata:
if (bytes)
- ratio = min(DIV_ROUND_UP(bytes, global_avail),
- PAGE_SIZE);
+ ratio = min(DIV_ROUND_UP(bytes / PAGE_SIZE, global_avail),
+ 100);
if (bg_bytes)
- bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail),
- PAGE_SIZE);
+ bg_ratio = min(DIV_ROUND_UP(bg_bytes / PAGE_SIZE, global_avail),
+ 100 - 1); /* bg_ratio should be less than ratio */
bytes = bg_bytes = 0;
--
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