On Fri, Oct 28, 2005 at 05:05:25PM +0100, Simon Riggs wrote: > 3. Helping Readahead efficiency: Currently blocks are allocated one at a > time. If many tables are extending at the same time, the blocks from > multiple tables will be intermixed together on the disk. Reading the > data back takes more head movement and reduces the I/O rate. Allocating
Ok, I agree with the rest but this isn't true. Any filesystem designed in the last ten years leaves gaps around the place so when you extend a file it remains consecutive. Some filesystems (like XFS) take it to extremes). Interleaving blocks with this pattern hasn't been done since FAT. That isn't to say that preextending isn't a good idea. With my pread() patch it was the one use of lseek() I couldn't remove. Other than that, good thought... Have a nice dat, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
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