Chris Ridd wrote: > On 30 Nov 2008, at 02:59, Bob Friesenhahn wrote: > > >> On Sun, 30 Nov 2008, Ian Collins wrote: >> >> >>> What did you expect? A 3GHz Opteron core takes about a minutes to >>> attempt to compress a 1GB .mkv file. So your P3 would probably take >>> between 5 and 10 minutes. Now move that to the kernel and your >>> system >>> will crawl. High gzip compressions are only really feasible on fast >>> multi-core systems (the compression is threaded). >>> >> The gzip manual pages says that the default compression level for gzip >> is -6. Experimentation will show that the compression ratio does not >> increase much at -9 so it is not worth it when you are short on time >> or CPU. >> > > Would it also help if the blocksize were reduced down from the default > (128K?) in the filesystem with gzip compression? > > It feels like it might - there'd be more (and smaller) blocks being > compressed, so more chance of other things being able to happen in > between blocks. > > Maybe not, there's be more starting and stopping going on. I'd expect there's an overhead doing that, rather than compressing more data in one go.
gzip compression works a lot better now the compression is threaded. It's a shame userland gzip isn't! -- Ian. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
