SquashFS developer Phillip Lougher posted a patch today just over one hundred lines of code yielding an outright massive performance gain for some operations with this compressed. read-only file-system.
The patch for SquashFS wires up SEEK_DATA and SEEK_HOLE support for much faster searchs for holes and data within sparse files. In cases of sparse copying of files with large holes, this can lead to very significant performance improvements for this file-system.
The benchmark shown by Lougher for a sparse copy of a big file with a massive hole yielded a wild improvement. Where the status quo took nearly 12 minutes, the 100+ lines of new code for SEEK_DATA/SEEK_HOLE handling took just 0.047 seconds. Or 15,277 times faster.
Quite a massive performance win for SquashFS when dealing with sparse files via this patch now under review on the Linux kernel mailing list.
