JFFS2 garbage collector blocking for minutes after mount

David Woodhouse dwmw2 at infradead.org
Sat Jul 23 11:07:18 EDT 2005

On Fri, 2005-07-22 at 16:47 +0200, Martin Egholm Nielsen wrote:
> 47695   idled                   384,63710
> 2997    nand_read_buf           62,43750
> 1122    nand_calculate_ecc      5,84380
> 677     __delay                 33,85000
> 502     nand_do_read_ecc        0,26370

Right, so we're spending most of that time actually reading the flash.
If you just read the entire flash device, how long does that take?
 (time dd if=/dev/mtd0 of=/dev/null) 

Artem's patch will improve things further by building up the fragtree
from newest to oldest node instead of from oldest to newest as we
currently do -- which actually means we don't need to check the CRC on
the oldest nodes before they never get added to the tree; we don't
actually need to read their data payload at all.

In the longer term, Ferenc's summary patch would decrease the amount of
reading from the flash even further. I keep meaning to go through that
in detail and make it mergeable.


More information about the linux-mtd mailing list