On Tue 06-03-07 12:23:22, Eric Sandeen wrote: > Jan Kara wrote: > > On Tue 06-03-07 06:36:09, Ulrich Drepper wrote: > >> Christoph Hellwig wrote: > >>> fallocate with the whence argument and flags is already quite complicated, > >>> I'd rather have another call for placement decisions, that would > >>> be called on an fd to do placement decissions for any further allocations > >>> (prealloc, write, etc) > >> Yes, posix_fallocate shouldn't be made more complicated. But I don't > >> understand why requesting linear layout of the blocks should be an > >> option. It's always an advantage if the blocks requested this way are > >> linear on disk. So, the kernel should always do its best to make this > >> happen, without needing an additional option. > > Actually, it's not that simple. You want linear layout of blocks you are > > going to read. That is not necessary a linear layout of blocks in a single > > file - trace sometime a start of some complicated app like KDE. You find > > it's seeking like a hell because it needs a few blocks from a ton of > > distinct files (shared libs, config files, etc). As these files are mostly > > read only, it's advantageous to interleave them on disk or at least keep > > them close. > > At some point shouldn't the apps be fixed, rather than do crazy things > with the filesystem? :) Yes :) That's basically what we told KDE developpers when they were complaining ;) But it's hard to fix it for them too (because of some desktop specs requiring lots of different text config files which can change anytime - don't ask me who designed it). Moreover for example for loading shared libraries from which you need just a few blocks scattered all over the place the problem is in ELF itself. I'll probably first write some userspace fs-reorganizer to find out how much these changes in layout are able to give you in performance (i.e. whether it's worth the effort of more complicated kernel online defragmenter). Honza -- Jan Kara <jack@xxxxxxx> SuSE CR Labs - 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
