On Aug 15, 2019, at 9:49 PM, Dongyang Li <dongyangli@xxxxxxx> wrote:
>
> For a bigalloc filesystem, converting the block bitmap from blocks
> to chunks in ext2fs_convert_subcluster_bitmap() can take a long time
> when the device is huge, because we test the bitmap
> bit-by-bit using ext2fs_test_block_bitmap2().
"bit-by-bit" can fit on the previous line.
> Use ext2fs_find_first_set_block_bitmap2() which is more efficient
> for mke2fs when the fs is mostly empty.
>
> e2fsck can also benifit from this during pass1 block scanning.
"benefit"
>
> Time taken for "mke2fs -O bigalloc,extent -C 131072 -b 4096" on a 1PB
> device:
>
> without patch:
> real 27m49.457s
> user 21m36.474s
> sys 6m9.514s
>
> with patch:
> real 6m31.908s
> user 0m1.806s
> sys 6m29.697s
>
> Signed-off-by: Li Dongyang <dongyangli@xxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
> ---
> lib/ext2fs/gen_bitmap64.c | 21 +++++++++------------
> 1 file changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
> index 6e4d8b71..97601232 100644
> --- a/lib/ext2fs/gen_bitmap64.c
> +++ b/lib/ext2fs/gen_bitmap64.c
> @@ -28,6 +28,7 @@
> #ifdef HAVE_SYS_TIME_H
> #include <sys/time.h>
> #endif
> +#include <sys/param.h>
>
> #include "ext2_fs.h"
> #include "ext2fsP.h"
> @@ -799,8 +800,8 @@ errcode_t ext2fs_convert_subcluster_bitmap(ext2_filsys fs,
> ext2fs_generic_bitmap_64 bmap, cmap;
> ext2fs_block_bitmap gen_bmap = *bitmap, gen_cmap;
> errcode_t retval;
> - blk64_t i, b_end, c_end;
> - int n, ratio;
> + blk64_t i, next, b_end, c_end;
> + int ratio;
>
> bmap = (ext2fs_generic_bitmap_64) gen_bmap;
> if (fs->cluster_ratio_bits == ext2fs_get_bitmap_granularity(gen_bmap))
> @@ -817,18 +818,14 @@ errcode_t ext2fs_convert_subcluster_bitmap(ext2_filsys fs,
> bmap->end = bmap->real_end;
> c_end = cmap->end;
> cmap->end = cmap->real_end;
> - n = 0;
> ratio = 1 << fs->cluster_ratio_bits;
> while (i < bmap->real_end) {
> - if (ext2fs_test_block_bitmap2(gen_bmap, i)) {
> - ext2fs_mark_block_bitmap2(gen_cmap, i);
> - i += ratio - n;
> - n = 0;
> - continue;
> - }
> - i++; n++;
> - if (n >= ratio)
> - n = 0;
> + retval = ext2fs_find_first_set_block_bitmap2(gen_bmap,
> + i, bmap->real_end, &next);
> + if (retval)
> + break;
> + ext2fs_mark_block_bitmap2(gen_cmap, next);
> + i = bmap->start + roundup(next - bmap->start + 1, ratio);
> }
> bmap->end = b_end;
> cmap->end = c_end;
> --
> 2.22.1
>
Cheers, Andreas
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