BeleniX enhancements now in OpenSolaris
By moinakg on Dec 14, 2007
A couple of new features introduced in BeleniX have now made their way into OpenSolaris core. These features are critical to making a LiveCD possible: Lofi compression and HSFS performance enhancements.
The second feature also benefits data CD/DVD usage on OpenSolaris in the generic case. The HSFS filesystem module in OpenSolaris used to issue I/O requests only in 2K chunks and had no readahead. This caused it to only achieve a max sequential read throughput of 3.5 MB/s whereas an 8X DVD for eg. is capable of supporting a much higher throughput. The changes as I had mentioned in earlier posts enable much better performance for both sequential and random access esp. on the newer faster boxes. There are a few other tweaks (like metadata prefetch) that I have in mind for later. The HSFS enhancements were integrated into Build 77. However subsequently there were a couple of problems that cropped up (a panic 6621609, and an issue with xVM 6627899) that had me slogging over 2 weekends to resolve these under tough deadlines.
Integrating lofi compression also required a lot of work over the original changes for BeleniX including a PSARC case (2007/569) and Alok Aggarwal did a fine job of this. This was integrated into Build 80. All this while lofi compression was only used in 32Bit mode since the BeleniX and Indiana microroots only have a 32Bit kernel till date. Testing and making lofi compression work in 64Bit mode had Alok breaking his head to figure out some weird rounding and data type issues. The code was cleaned up and enhanced a lot in addition to making the compression algorithm pluggable so that additional compression techniques can be supported in future, if desired.