On Mon 27-11-17 16:06:50, Yafang Shao wrote:
> +cc fcicq
[...]
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 8a15511..6c5c018 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -377,7 +377,16 @@ static unsigned long global_dirtyable_memory(void)
> if (!vm_highmem_is_dirtyable)
> x -= highmem_dirtyable_memory(x);
>
> - return x + 1; /* Ensure that we never return 0 */
> + /*
> + * - Why 100 ?
> + * - Because the return value will be used by dirty ratio and
> + * dirty background ratio to calculate dirty thresh and bg thresh,
> + * so if the return value is two small, the thresh value maybe
> + * calculated to 0.
> + * As the max value of ratio is 100, so the return value is added
> + * by 100 here.
> + */
> + return x + 100;
No. We should just revert 0f6d24f87856 ("mm/page-writeback.c: print a
warning if the vm dirtiness settings are illogical") because it is of a
dubious value and it causes problems. I am not even sure why it got
merged. It doesn't have any ack or review and I remember objecting to
the patch previously as pointless.
--
Michal Hocko
SUSE Labs
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