ubifs: sync() causes writes even if nothing is changed
dedekind1 at gmail.com
Wed Oct 20 09:26:58 EDT 2010
On Wed, 2010-10-13 at 18:30 +0200, Hans J. Koch wrote:
> Running this command:
> # while true ; do sync; sleep 1; done
> causes two eraseblocks being erased every second, although there
> are no writes to the ubifs filesystem. I hacked some printks into
> my NAND driver that print page_address and column for each erase.
> With that, I get this output every second:
> [ 63.701765] erase p=0x0000ae40 c=0xffffffff
> [ 63.706534] erase p=0xffffffff c=0xffffffff
> [ 63.725492] erase p=0x0000ae80 c=0xffffffff
> [ 63.730260] erase p=0xffffffff c=0xffffffff
> From a quick glance at the ubifs code, this might come out of the
> garbage collector that is triggered on every sync() and writes
> something even if nothing has changed.
> Is that really needed?
I briefly looked, and UBIFS is doing a lot of I/O in that case, which is
unnecessary and should not be done, I'll need to investigate this.
Artem Bityutskiy (Артём Битюцкий)
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