From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750955AbdKHIwp (ORCPT ); Wed, 8 Nov 2017 03:52:45 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:48757 "EHLO huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750720AbdKHIwn (ORCPT ); Wed, 8 Nov 2017 03:52:43 -0500 Subject: Re: [f2fs-dev] [PATCH] f2fs: optimize the way of traversing free_nid_bitmap To: Fan Li , "'Chao Yu'" , "'Jaegeuk Kim'" CC: , References: <002201d357b9$adf558a0$09e009e0$@samsung.com> From: Chao Yu Message-ID: <17b70863-a406-45c5-c94a-27fda486c66e@huawei.com> Date: Wed, 8 Nov 2017 16:52:21 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <002201d357b9$adf558a0$09e009e0$@samsung.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017/11/7 19:14, Fan Li wrote: > We call scan_free_nid_bits only when there isn't many > free nids left, it means that marked bits in free_nid_bitmap > are supposed to be few, use find_next_bit_le is more > efficient in such case. > According to my tests, use find_next_bit_le instead of > test_bit_le will cut down the traversal time to one > third of its original. > > Signed-off-by: Fan li Reviewed-by: Chao Yu Thanks, > --- > fs/f2fs/node.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > index fef5c68..d234c6e 100644 > --- a/fs/f2fs/node.c > +++ b/fs/f2fs/node.c > @@ -1955,6 +1955,7 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi) > struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA); > struct f2fs_journal *journal = curseg->journal; > unsigned int i, idx; > + nid_t nid; > > down_read(&nm_i->nat_tree_lock); > > @@ -1964,10 +1965,10 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi) > if (!nm_i->free_nid_count[i]) > continue; > for (idx = 0; idx < NAT_ENTRY_PER_BLOCK; idx++) { > - nid_t nid; > - > - if (!test_bit_le(idx, nm_i->free_nid_bitmap[i])) > - continue; > + idx = find_next_bit_le(nm_i->free_nid_bitmap[i], > + NAT_ENTRY_PER_BLOCK, idx); > + if (idx >= NAT_ENTRY_PER_BLOCK) > + break; > > nid = i * NAT_ENTRY_PER_BLOCK + idx; > add_free_nid(sbi, nid, true); > @@ -1980,7 +1981,6 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi) > down_read(&curseg->journal_rwsem); > for (i = 0; i < nats_in_cursum(journal); i++) { > block_t addr; > - nid_t nid; > > addr = le32_to_cpu(nat_in_journal(journal, i).block_addr); > nid = le32_to_cpu(nid_in_journal(journal, i)); >