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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@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
debian-1.42.9
Theodore Ts'o 2012-11-24 19:02:48 -05:00
parent c3f9641eaf
commit b65ccfc7a4
1 changed files with 23 additions and 4 deletions
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27
lib/ext2fs/blkmap64_rb.c
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@ -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)
break;
if (pos < start) {
count -= start - pos;
if (count < 0)
continue;
pos = start;
}
if (pos + count > start + num)
count = start + num - pos;
while (pos < (ext->start + ext->count)) {
if ((pos - start) >= num)
return 0;
while (count > 0) {
if ((count >= 8) &&
((pos - start) % 8) == 0) {
int nbytes = count >> 3;
int offset = (pos - start) >> 3;
memset(out + offset, 0xFF, nbytes);
pos += nbytes << 3;
count -= nbytes << 3;
continue;
}
ext2fs_fast_set_bit64((pos - start), out);
pos++;
count--;
}
}
return 0;