Re: JFFS2 garbage collector blocking for minutes after mount

David Woodhouse
2005-07-23T15:07:18Z

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.

--
dwmw2