On Fri, Oct 13, 2006 at 02:10:02AM -0600, Andreas Dilger wrote: > On Oct 11, 2006 09:55 -0400, Theodore Ts'o wrote: > > Block allocation clusters > > ========================= > > The basic idea is that we store in the superblock the size of a block > > allocation cluster, and that we change the allocation algorithm and the > > preallocation code to always try to allocate blocks so that whenever > > possible, an inode will use contiguous clusters of blocks, which are > > aligned in multiples of the cluster size. > > As mentioned in the weekly conference call - Alex has already implemented > this as part of the mballoc code that CFS uses in conjunction with extents. > There is a /proc tunable for the cluster size, which currently defaults to > 1MB clusters (the Lustre RPC size) to optimize performance for RAID systems. > The allocations are aligned with the LUN so that an integer number of RAID > stripes are modified for a write. Smaller allocation chunks are packed > together. I suggest this be tunable by superblock field, and not by a /proc tunable. This is the sort of thing which might be different per-filesystem, and the algorithm will be most effective if the filesystem always use the same cluster size from the time when it was first created. I'd be happy to assign a superblock field for this purpose, and add the appropriate tune2fs support if we have general agreement on this point. > Alex is working to update the multi-block allocator for the 2.6.18 kernel, > in conjunction with delayed allocation for ext4, and will hopefully have > a patch soon. Great! - Ted - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
