Countx with summarize very slowly

Hi, 

 I work in DorectQuery Mode. 
i have two tables in my model : 

- Fact table with a lot of row

- Calendar table that is connect to Fact table.

i this following measures in Power BI (they are all measure type columns and not calculated columns) : 

1 - I create a cumulative sum

2 - I create a measure which count number of reference in my model :

DISTINCT REFERENCE = DISTINCTCOUNT(REFERENCE)

3 - i create a third measure which count number of reference with cumul <>0

COUNTX(summarize(FILTER('TABLE_FACT','TABLE_FACT'[RUNNING_TOTAL]<>0),TABLE_FACT[REFERENCE]),[DISTINCT REFERENCE])

My problem is with third measure . When I put this measure in the card , it's take a long time to load (5 minutes). 

Have you an idea for speed up this third measure ? 

Thanks you