On Sat, 24 Nov 2012, Theodore Ts'o wrote:
> Date: Sat, 24 Nov 2012 19:36:33 -0500
> From: Theodore Ts'o <tytso@xxxxxxx>
> To: Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Subject: [PATCH 5/6] libext2fs: optimize rb_get_bmap_range() for mostly
> allocated bmaps
>
> This optimizies the CPU utilization of the rb_get_bmap_range()
> function when most of the bitmap is allocated.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> lib/ext2fs/blkmap64_rb.c | 29 ++++++++++++++++++++++++-----
> 1 file changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c
> index 0705cf2..3a5518b 100644
> --- a/lib/ext2fs/blkmap64_rb.c
> +++ b/lib/ext2fs/blkmap64_rb.c
> @@ -721,6 +721,7 @@ static errcode_t rb_get_bmap_range(ext2fs_generic_bitmap bitmap,
> struct rb_node *parent = NULL, *next, **n;
> struct ext2fs_rb_private *bp;
> struct bmap_rb_extent *ext;
> + int count;
> __u64 pos;
>
> bp = (struct ext2fs_rb_private *) bitmap->private;
> @@ -748,14 +749,32 @@ static errcode_t rb_get_bmap_range(ext2fs_generic_bitmap bitmap,
> ext = ext2fs_rb_entry(parent, struct bmap_rb_extent, node);
>
> pos = ext->start;
> - if (pos < start)
> + count = ext->count;
> + if (pos > start+num)
Missing spacing around '+'.
Also I think that the condition should rather be:
if (pos >= start + num)
> + break;
> + if (pos < start) {
> + count -= start - pos;
> + if (count < 0)
> + continue;
> pos = start;
> -
> - while (pos < (ext->start + ext->count)) {
> - if ((pos - start) >= num)
> - return 0;
> + }
> + if (pos+count > start+num)
> + count = start+num - pos;
missing spacing around '+'
> +
> + while (count > 0) {
> + if ((count >= 8) &&
> + ((pos - start) % 8) == 0) {
> + int nbytes = count >> 3;
> + int offset = (pos -start) >> 3;
missing spacing around '-'
> +
> + memset(out + offset, 0xFF, nbytes);
> + pos += nbytes << 3;
> + count -= nbytes << 3;
> + continue;
> + }
> ext2fs_fast_set_bit64((pos - start), out);
> pos++;
> + count--;
> }
> }
> return 0;
>
--
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