Hi Jaegeuk,
On 07/02/2014 06:30 PM, Jaegeuk Kim wrote:
> 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.
Agree.
>
> Well, IMO the former case would be a little bit more common.
>
> Gu,
> Can you provide some performance numbers wrt this?
OK. I'll do it.:)
Thanks,
Gu
>
> 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.fnst@xxxxxxxxxxxxxx>
>> ---
>> 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
>
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