Andreas Dilger wrote: > One of the issues is that w/o delalloc the mballoc code only gets > single-block allocations, so there might be a problem with the interface > to mballoc. That might be caused by the fact the patches were changed > at one point from delalloc-atop-mballoc to mballoc-atop-delalloc, and > something was missed in that conversion. I've been testing this with a 16x1MB buffered dd to a fresh filesystem; it gets 7 extents, and out of order. :( First block: 37120 Last block: 63427 Discontinuity: Block 1024 is at 38400 (was 38143) Discontinuity: Block 1036 is at 57344 (was 38411) Discontinuity: Block 2048 is at 38412 (was 58355) Discontinuity: Block 2072 is at 61440 (was 38435) Discontinuity: Block 3072 is at 38436 (was 62439) Discontinuity: Block 3108 is at 62440 (was 38471) /mnt/test/testfile: 7 extents found One thing that seems to be happening is that thanks to delalloc, a nice big request is coming in (only 1036 blocks of the 4096, not quite sure why), but then it gets into ext4_mb_normalize_request(), which finds the most blocks it can "preallocate" is 256, and chops down the request to 256 blocks. Shouldn't this preallocation be over & above what was asked for, vs. reducing the request? Ok, so, we get allocations in 256-block chunks... Why they don't all come out contiguous, I don't know yet... -Eric - 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
