[Yaffs] Collecting page

Hi,

Can someone explain what happens here?
If I store files on my nand flash, suddenly I see following output printed out (see below).
This causes a lot of delay when writing files. What's happening, and can this be avoided?

...
store: /nand/music.mp3
GC Selected block 20 with 8 free, prioritised:0
yaffs: GC erasedBlocks 8 aggressive 1
Collecting block 20, in use 56, shrink 0,
Collecting page 0, 563 4 2048
Allocated block 21, seq 4125, 7 left
Collecting page 2, 573 1 2048
Collecting page 3, 573 2 2048
Collecting page 4, 573 3 2048
Collecting page 5, 573 4 2048
Collecting page 6, 573 5 556
Collecting page 7, 573 0 0
Collecting page 9, 583 1 2048
Collecting page 10, 583 2 2048
Collecting page 11, 583 3 2048
Collecting page 12, 583 4 2048
Collecting page 13, 583 5 556
Collecting page 14, 583 0 0
Collecting page 16, 258 1 2048
Collecting page 17, 258 2 2048
Collecting page 18, 258 3 2048
Collecting page 19, 258 4 2048
Collecting page 20, 258 5 2048
Collecting page 21, 258 6 209
Collecting page 22, 258 0 0
Collecting page 24, 524 1 2048
Collecting page 25, 524 2 2048
Collecting page 26, 524 3 2048
Collecting page 27, 524 4 2048
Collecting page 28, 524 5 2048
Collecting page 29, 524 6 2048
Collecting page 30, 524 7 2048
Collecting page 31, 524 8 554
Collecting page 32, 524 0 0
Collecting page 34, 534 1 2048
Collecting page 35, 534 2 2048
Collecting page 36, 534 3 2048
Collecting page 37, 534 4 2048
Collecting page 38, 534 5 167
Collecting page 39, 534 0 0
Collecting page 41, 544 1 2048
Collecting page 42, 544 2 2048
Collecting page 43, 544 3 2048
Collecting page 44, 544 4 1693
Collecting page 45, 544 0 0
Collecting page 47, 554 1 2048
Collecting page 48, 554 2 2048
Collecting page 49, 554 3 2048
Collecting page 50, 554 4 2048
Collecting page 51, 554 5 2048
Collecting page 52, 554 6 2048
Collecting page 53, 554 7 2048
Collecting page 54, 554 8 1337
Collecting page 55, 554 0 0
Collecting page 57, 564 1 2048
Collecting page 58, 564 2 2048
Collecting page 59, 564 3 2048
Collecting page 60, 564 4 2048
Collecting page 61, 564 5 1473
Collecting page 62, 564 0 0
Collecting page 63, 574 0 0
yaffs_BlockBecameDirty block 20 state 8
Erased block 20
...


Kind regards,
Stijn.