Claudio Freire composed on 2015-01-20 00:58 (UTC-0300):
it's not even clear doing what the fate indicates would improve write cycle efficiency, it may even make it worse (say, if the update script merely left the new file in place, and updated the timestamps on the old files repeatedly causing more metadata flushes).
There's still communication failure here. My interest is in why there is any write at all when file content before and after update process is identical. Maybe fstab makes the better example, since the stub of it in some rpm is obviously not going to work as-is on an already installed and configured installation. It too is a small file, so RAM should be sufficient for update process to work whatever magic it attempts.
I don't understand why you wrote this. I'm not at all concerned about efficiency here except as writing any sector at all is unnecessary. The file was not changed, so why the write?
Because batched writes get written in one flash sector (usually 2MB), and can contain more than one filesystem block.
I don't understand why this would be relevant to my question. One single sector file could be the difference between 2 batches and 1 batch.
Writes, even random writes, on a block device backed by flash usually results in one single write cycle on one block. That's wear leveling at work.
Basically, count how many bytes (blocks?) in total are written to disk while updating, and unless you can significantly decrease that number, which files get touched matter less.
Again I don't get it. Writes are slower I/O than reads. In the case of file not changed, why any write at all?
If you write one block at all, the remaining 511 will usually be for free.
So, why make a huge effort to avoid writing a few blocks if it's not going to report any benefit?
Huge effort? A few here, a few there. Maybe it doesn't seem so with electrons, but it does consume energy to make them move. Waste not, want not.
It should all start from the lowest hanging fruit.
It makes little sense to go for the highest first.
I only ever thought about $SUBJECT as a result of remembering the FATE. Here is a possibility of hitting multiple targets hit with one shot, instituting policy that induces less waste.
For another example, new installations should use relatime by default.
How that is better than noatime, which I started using long before ever hearing about relatime, I never figured out. -- "The wise are known for their understanding, and pleasant words are persuasive." Proverbs 16:21 (New Living Translation) Team OS/2 ** Reg. Linux User #211409 ** a11y rocks! Felix Miata *** http://fm.no-ip.com/ -- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-factory+owner@opensuse.org