possibilities with raw flash access [LWN.net]

possibilities with raw flash access

Posted Aug 22, 2009 20:13 UTC (Sat) by phip (guest, #1715)
In reply to: possibilities with raw flash access by dlang
Parent article: The trouble with discard

> leave the unused space at the end of a block is left as all '1's
> rather than all '0's so that additional data could be appended
> without needing to erase a block first.

> change it's 'nothing more to point to' from a pointer containing
> all 0s to a pointer containing all 1s so that adding an additional
> block to a chain (or extent..) would not require re-writing the
> prior block as well

Would simply inverting the raw data from/to the flash device
before/after doing any block device or filesystem processing
be a useful optimization?

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possibilities with raw flash access

Posted Aug 22, 2009 20:27 UTC (Sat) by dlang (✭ supporter ✭, #313) [Link]

two things

it would only help if the device is smart enough to not allocate a new block on the flash (requiring a erase of a block eventually) if the data changes are only 1->0

inverting all the data will thrash your cpu cache, and most things don't benefit from the change, so I think it would be smarter to modify the filesystem