Hi Santyago, apologies if this seems redundant, but just to clarify, the results you posted originally were with CPU and EMC frequencies set to maximum?
By further investigation, with less data size, comes less speed.
Have you tried to test with other DD_BLKSIZES, such as 512K?
Supposed the result should be closed the emmc 5.1 spec with maximum speed of sequential write about 125MB/s and sequential read about 250MB/s