Am Dienstag, 29. Januar 2013, 10:15:49 schrieb Russell King - ARM Linux:
On Mon, Jan 28, 2013 at 02:25:10PM -0800, Andrew Morton wrote:
What's this "with enabled unaligned memory access" thing? You mean "if the arch supports CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS"? If so, that's only x86, which isn't really in the target market for this patch, yes?
It's a lot of code for a 50ms boot-time improvement. Does anyone have any opinions on whether or not the benefits are worth the cost?
Well... when I saw this my immediate reaction was "oh no, yet another decompressor for the kernel". We have five of these things already. Do we really need a sixth?
My feeling is that we should have: - one decompressor which is the fastest - one decompressor for the highest compression ratio - one popular decompressor (eg conventional gzip)
the problem gets more complicated as the "fastest" decompressor usually creates larger images which need more time to load from the storage, e.g. a one MB larger image on a 10 MB/s storage (note: bootloaders often configure the storage controllers in slow modes) gives 100 ms more boot time, thus eating the gain of a "fast decompressor".
Yes, the larger image could matter. Definitely it takes longer.
Here are some updated test cases: Including "loading time"
lzo lz4 loading time: 480ms 510ms decompression time: 336ms 180ms(with efficient unaligned memory access enabled and ARM optimization) total time: 816ms 690ms
lz4 is still 15% faster in total time. This one is similar to the simulated result by Russell King.
