On Wed, 16 May 2007 15:36:44 +0300, Pekka Enberg wrote: > On 5/16/07, Jörn Engel <joern@xxxxxxxxxxxxxxx> wrote: > > > >More trouble? > > Forgot to add (see below). Seems logfs_segment_read would be simpler > too if you fixed this. Would it? I think that code would still be needed, although possibly in a different function. There are two minor drawbacks to using the page cache, btw: - Indirect blocks need some mapping too. So either I need to steal a bit from the inode space or from the fpos space. - OOM handling is a bit more complicated. I would need a mempool for that. > >[ Objects are the units that get compressed. Segments can contain both > >compressed and uncompressed objects. ] > > > >It is a trade-off. Each object has a 24 Byte header plus X Bytes of > >data. Whether the data is compressed or not is indicated in the header. > > Was my point really. Why do segments contain both compressed and > uncompressed objects? Compressing random data will actually enlarge it. If that happens I simply store the verbatim uncompressed data instead and mark it as such. There is also demand for a user-controlled bit in the inode to disable compression completely. All those .jpg, .mpg, .mp3, etc. just waste time by trying and failing to compress them. Jörn -- Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. -- Doug MacIlroy - 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
