Free the whole range rather than bits [LWN.net]

Free the whole range rather than bits

Posted Jun 21, 2014 13:52 UTC (Sat) by alonz (subscriber, #815)
In reply to: Free the whole range rather than bits by niner
Parent article: The volatile volatile ranges patch set

I suspect the cost of refreshing just one page from the JPEG from the 'net will tend to be almost the same as refreshing the entire image… and refreshing two (disjoint) pages will almost certainly cost more than the entire image.

Of course, these are just my estimates; they may be wrong in the particular, but I've personally designed systems that did exhibit this behavior. An obvious example is when caching a compressed version of some resource — restarting compression from the middle is far harder than redoing it all from scratch.

to post comments

Free the whole range rather than bits

Posted Jun 26, 2014 6:28 UTC (Thu) by dlang (guest, #313) [Link] (1 responses)

remember that this is less for caching data from the net and more for caching the uncompressed images for faster display.

so it's more likely to be 4K out of a uncompressed image that the app would just need to pull the appropriate range of data out of the .jpg that it has stored elsewhere.

Free the whole range rather than bits

Posted Jun 26, 2014 10:52 UTC (Thu) by alonz (subscriber, #815) [Link]

Even for this use-case, I suspect repeating the entire decompression would still cost less (and have less bugs) than trying to reconstruct a single page from the middle of the image. And more modern formats (e.g. WebP) make the challenge even greater.