Thanks Changman for reminding this. :) If there are a lot of ones in the bit stream, find_next_bit_le would cause some overhead to translate the bits.
However, it would be effective to use find_next_bit_le if the bit stream looks like 0000000001. Well, IMO the former case would be a little bit more common. Gu, Can you provide some performance numbers wrt this? On Tue, Jun 24, 2014 at 06:20:41PM +0800, Gu Zheng wrote: > Use find_next_bit_le rather than test_bit_le to improve search speed > lightly. > > Signed-off-by: Gu Zheng <guz.f...@cn.fujitsu.com> > --- > fs/f2fs/dir.c | 43 +++++++++++++++++++++---------------------- > 1 files changed, 21 insertions(+), 22 deletions(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 3edd561..ba510fb 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -93,42 +93,41 @@ static struct f2fs_dir_entry *find_in_block(struct page > *dentry_page, > const char *name, size_t namelen, int *max_slots, > f2fs_hash_t namehash, struct page **res_page) > { > - struct f2fs_dir_entry *de; > - unsigned long bit_pos = 0; > + unsigned long bit_pos = 0, bit_start = 0; > struct f2fs_dentry_block *dentry_blk = kmap(dentry_page); > const void *dentry_bits = &dentry_blk->dentry_bitmap; > - int max_len = 0; > > - while (bit_pos < NR_DENTRY_IN_BLOCK) { > - if (!test_bit_le(bit_pos, dentry_bits)) { > - if (bit_pos == 0) > - max_len = 1; > - else if (!test_bit_le(bit_pos - 1, dentry_bits)) > - max_len++; > - bit_pos++; > - continue; > + while (bit_start < NR_DENTRY_IN_BLOCK) { > + struct f2fs_dir_entry *de; > + int max_len = 0; > + > + bit_pos = find_next_bit_le(dentry_bits, > + NR_DENTRY_IN_BLOCK, bit_start); > + > + max_len = bit_pos - bit_start; > + if (max_len > *max_slots) { > + *max_slots = max_len; > + max_len = 0; > } > + > + if (bit_pos >= NR_DENTRY_IN_BLOCK) > + break; > + > de = &dentry_blk->dentry[bit_pos]; > if (early_match_name(name, namelen, namehash, de)) { > if (!memcmp(dentry_blk->filename[bit_pos], > name, namelen)) { > *res_page = dentry_page; > - goto found; > + return de; > } > } > - if (max_len > *max_slots) { > - *max_slots = max_len; > - max_len = 0; > - } > - bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len)); > + > + bit_start = bit_pos > + + GET_DENTRY_SLOTS(le16_to_cpu(de->name_len)); > } > > - de = NULL; > kunmap(dentry_page); > -found: > - if (max_len > *max_slots) > - *max_slots = max_len; > - return de; > + return NULL; > } > > static struct f2fs_dir_entry *find_in_level(struct inode *dir, > -- > 1.7.7 -- Jaegeuk Kim ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel