Re: [PATCH] ubi: Select fastmap anchor PEBs considering wear level rules

[Richard Weinberger <richard.weinberger@xxxxxxxxx>]

On Thu, Apr 30, 2020 at 10:34 AM Arne Edholm <arne.edholm@xxxxxxxx> wrote:
> Are you satisfied with my answers or are there additional
> information/changes needed?

Yes. In the meanwhile I did more testing and with your changes the
anchor PEB selection
is *much* better. Testing took some time and then I scheduled away to
other stuff...
Critical workloads are these where a fastmap is not written due to
heavy write load,
but other events like volume change/creation.

A good reproducer seems something stupid like that:
for i in `seq 1000` ; do ubimkvol -N test -m /dev/ubi0 >/dev/null &&
ubirmvol /dev/ubi0 -n 0 ; done
Wearleveling threshold is 50, btw.

Without your patch, the erase counter of the first 64 PEBs:
4    4    4    4    4    4    4    4
4    4    4    4    4    4    4    4
4    4    4    4    4    4    4    4
4    4    4    4    4    4    4    4
4    4    4    4    4    4    4    4
4    4    4    4    4    4    22   4
4    19   4    4    4    4    4    4
4    4    4    4    8    908  906  1

And with your patch:
95   95   95   95   95   95   95   95
95   95   95   95   95   95   95   95
95   95   95   95   95   95   95   95
95   95   95   95   95   95   95   95
95   95   95   95   95   95   95   95
95   95   95   95   95   95   95   95
95   95   95   94   94   94   94   94
94   94   94   94   94   94   94   95

In tests where the volumes are just filled and erased again, I could
not see a difference.

So, your patch will be part of the next merge window. :-)

-- 
Thanks,
//richard

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