-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 3/13/2013 4:16 PM, Theodore Ts'o wrote: > If we want to optimize the time to copy said sparse file, and if > we assume that by the time we are defragging said sparse file, we > are done doing writes which will allocate new blocks, then having > defrag optimize the file so that when the extents are sorted by > logical block number, the physical block numbers are contiguous, > then that's probably the best "figure of merit" to use. And I'll > note that right now that's what filefrag is reporting, and what I > think e4defrag should be changed to use when deciding whether the > donor file is "better" than the original file. That's certainly exactly what I expect to get after defragging a file. > But that's not necessarily the only way to measure extents, and > the current e4defrag code is clearly of the opinion that if the > file is using a contiguous region of blocks, even if the blocks > were allocated "backwards", that there's no point defragging the > file, since after all, if the file was written in such a random > order with respect to logical block numbers, it will probably be > read in a random order, so keeping the file blocks used contiguous > to minimize free block fragmentation is the best thing to shoot > for. That seems wrong to me. It shouldn't matter what condition the file starts in; the end should always be a file with blocks allocated in the proper order. If there's no point in defragging a randomly accessed file, then the user shouldn't bother running defrag on it, and conversely, if they do, it should perform the task they requested. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJRSLIeAAoJEJrBOlT6nu7526UH/RTFmZWDXgrzGUwbbBJ1IN6t aylOR1Wg3SWKEp5Cs717iHCNPMosF31bHkHG+MbpoSvJpAfRPZ7svTDTbzfBZ17F dLKLOAYx3KRBeX8TSYIC7e5E/qTg1C6wmiS1Rlab5boeRkmUL/kP7WPpCgKHpydZ tgUtzO7npCWVxP3eG9NnOR9y9U0PHuS3B9Q5S2vhbeqpxQnEi4cphoSw1bOJVcCj RkddmEUuj+usDl8kHwxlyoiRhcwMUY59UuTqEWqgDkntQL5DTdX//AfrUdW3PBmB DKIC4dCaoivXoKarKRuLaHM04rldOvZdxNFFNnoKlnQMhh4i82RnEYSio26778c= =0Iea -----END PGP SIGNATURE----- -- 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
