uclinux : how to flush filesystem cache

Hi all,

I use uClinux NoMMU and a filesystem to write / read on a sd card.

My problem is that I have a writing speed of 1MB/s and after some write commands I have the cache full even after sync() command.

(I checked that the sd card is mounted)

/ mnt / Applications> free
MemTotal: 127524 kB
MemFree: 80484 kB
Buffers: 7728 kB
/ mnt / Applications> free
MemTotal: 127524 kB
MemFree: 65172 kB
Buffers: 7732 kB
/ mnt / Applications> free
MemTotal: 127524 kB
MemFree: 57108 kB
Buffers: 7736 kB
.... after some write command
/ mnt / sd> free
MemTotal: 127524 kB
MemFree: 2064 kB
Buffers: 360 kB

so my question is how to clear the cache after sync sd card?

thanks for help

Regards

Hayder