From mboxrd@z Thu Jan 1 00:00:00 1970 From: Changman Lee Subject: Re: [PATCH 3/4] f2fs: use find_next_bit_le rather than test_bit_le in, find_in_block Date: Wed, 02 Jul 2014 16:49:03 +0900 Message-ID: <20140702074903.GA7854@cm224.lee> References: <53A950F9.907@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jaegeuk Kim , f2fs , fsdevel To: Gu Zheng Return-path: Received: from mailout1.samsung.com ([203.254.224.24]:32700 "EHLO mailout1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750809AbaGBHuf (ORCPT ); Wed, 2 Jul 2014 03:50:35 -0400 Received: from epcpsbgr1.samsung.com (u141.gpu120.samsung.co.kr [203.254.230.141]) by mailout1.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0N82006QZR48G750@mailout1.samsung.com> for linux-fsdevel@vger.kernel.org; Wed, 02 Jul 2014 16:50:33 +0900 (KST) Content-disposition: inline In-reply-to: <53A950F9.907@cn.fujitsu.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hi, Gu Unfortunately, find_next_bit isn't always better than test_bit. Refer to commit 5d0c667121bfc8be76d1580f485bddbe73465d1a I remember that Perviously, Jaegeuk had changed find_next_bit to test_bit because find_next_bit spent much cpu time in the case of there is lot of dentries like a postmark. Sorry, I should have reported this quickly. 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 > --- > 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