[Yaffs] It takes long to write to a large file

The log below is for the test of writing 40 MB file. My questions are
1) Why does it take much longer for YAFFS2 to write the same 40 MB file compared to JFFS2?
2) After writing the file, I remove the file and write it again. Why does it take much longer?

At the moment, I can only think of one reason. JFFS2 compressed the data before writing to flash, so for

1) JFFS2 writes much less data and it takes less time.
2) After deleting the file, eraseing the flash is deferred to the subsequent writes. Because YAFFS2 data is uncompressed, it takes more time to erase more data.

For YAFFS2:

# time ./write_fs 41943040 1

 real    0m39.000s
 user    0m1.130s
 sys     0m37.850s
 # ls /mnt
 02800000_0  lost+found
 # rm /mnt/02800000_0
 # time ./write_fs 41943040 1

 real    0m56.710s
 user    0m1.120s
 sys     0m55.590s
 # rm /mnt/02800000_0
 # time ./write_fs 41943040 1

 real    0m57.810s
 user    0m1.070s
 sys     0m56.740s
 # rm /mnt/02800000_0
 # time ./write_fs 41943040 1

 real    0m55.740s
 user    0m1.110s
 sys     0m54.630s

For JFFS2:
                    # time ./write_fs 41943040 1

 real    0m9.940s
 user    0m1.130s
 sys     0m8.810s
 # rm /mnt/02800000_0
 # time ./write_fs 41943040 1

 real    0m9.940s
 user    0m1.150s
 sys     0m8.780s
 # rm /mnt/02800000_0
 # time ./write_fs 41943040 1

 real    0m10.510s
 user    0m1.040s
 sys     0m8.900s

        
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