On 2010-12-09 Phillip Lougher wrote: > + stream->state = xz_dec_init(XZ_PREALLOC, block_size); This sets the preallocated LZMA2 dictionary size to Squashfs block size, which allows the best compression ratio for the given block size (bigger values would be waste of memory). XZ decompressor needs about 30 KiB of memory plus the dictionary. So with 1 MiB Squashfs block size a little over 1 MiB of memory is needed by the XZ decompressor. Would it be useful to support smaller dictionaries without reducing the Squashfs block size? It would save RAM while increasing the Squashfs image size less than if also the block size was reduced. Reasonable dictionary sizes could be e.g. 75 %, 50 %, or 25 % of the Squashfs block size. The size increase of the Squashfs image will vary a lot depending on the files in it, but e.g. dict_size = block_size / 2 won't necessarily increase the image size more than 1 %. I don't know if this kind of RAM savings matter on embedded systems. I hope someone else can comment. My point in this email is only to let others know that reducing the RAM usage is possible without reducing the Squashfs block size. -- Lasse Collin | IRC: Larhzu @ IRCnet & Freenode -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
