2017-11-27 16:21 GMT+08:00 Michal Hocko <mhocko@xxxxxxxx>:
> 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.
> --
It is reviewed and merged by Andrew.
>From Andrew:
> I think this means that a script which alters both dirty_bytes and
dirty_background_bytes must alter dirty_background_bytes first if they
are being decreased and must alter dirty_bytes first if they are being
increased. Or something like that.
It will help us to find the error if we don't change these values like this.
Thanks
Yafang
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
