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From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: dsterba@suse.cz, Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 04/19] btrfs: remove the open-code to read disk-key
Date: Thu, 17 Sep 2020 16:02:37 +0800	[thread overview]
Message-ID: <e5a6d6a4-93b7-9845-5448-ac56ecf97075@gmx.com> (raw)
In-Reply-To: <20200916160115.GN1791@twin.jikos.cz>


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On 2020/9/17 上午12:01, David Sterba wrote:
> On Tue, Sep 15, 2020 at 01:35:17PM +0800, Qu Wenruo wrote:
>> generic_bin_search() distinguishes between reading a key which doesn't
>> cross a page and one which does. However this distinction is not
>> necessary since read_extent_buffer handles both cases transparently.
>>
>> Just use read_extent_buffer to streamline the code.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>  fs/btrfs/ctree.c | 13 ++-----------
>>  1 file changed, 2 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
>> index cd1cd673bc0b..e204e1320745 100644
>> --- a/fs/btrfs/ctree.c
>> +++ b/fs/btrfs/ctree.c
>> @@ -1697,7 +1697,6 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
>>  	}
>>  
>>  	while (low < high) {
>> -		unsigned long oip;
>>  		unsigned long offset;
>>  		struct btrfs_disk_key *tmp;
>>  		struct btrfs_disk_key unaligned;
>> @@ -1705,17 +1704,9 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
>>  
>>  		mid = (low + high) / 2;
>>  		offset = p + mid * item_size;
>> -		oip = offset_in_page(offset);
>>  
>> -		if (oip + key_size <= PAGE_SIZE) {
>> -			const unsigned long idx = offset >> PAGE_SHIFT;
>> -			char *kaddr = page_address(eb->pages[idx]);
>> -
>> -			tmp = (struct btrfs_disk_key *)(kaddr + oip);
>> -		} else {
>> -			read_extent_buffer(eb, &unaligned, offset, key_size);
>> -			tmp = &unaligned;
>> -		}
>> +		read_extent_buffer(eb, &unaligned, offset, key_size);
>> +		tmp = &unaligned;
> 
> Reading from the first page is a performance optimization on systems
> with 4K pages, ie. the majority. I'm not in favor removing it just to
> make the code look nicer.
> 

For 4K system, with the optimization it only saves one
read_extent_buffer() call cost.

In read_extent_buffer() it's still doing the same thing.

Or we will need to manually call get_eb_page_offset() here to make it
work for subpage.

I wonder if it really worthy.

Thanks,
Qu


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  reply	other threads:[~2020-09-17  8:10 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15  5:35 [PATCH v2 00/19] btrfs: add read-only support for subpage sector size Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 01/19] btrfs: extent-io-tests: remove invalid tests Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 02/19] btrfs: remove the unnecessary parameter @start and @len for check_data_csum() Qu Wenruo
2020-09-15  8:39   ` Johannes Thumshirn
2020-09-15  5:35 ` [PATCH v2 03/19] btrfs: calculate inline extent buffer page size based on page size Qu Wenruo
2020-09-15  8:35   ` Nikolay Borisov
2020-09-15 10:05     ` Qu Wenruo
2020-09-15  8:40   ` Johannes Thumshirn
2020-09-15  5:35 ` [PATCH v2 04/19] btrfs: remove the open-code to read disk-key Qu Wenruo
2020-09-15  8:36   ` Nikolay Borisov
2020-09-15  8:40   ` Johannes Thumshirn
2020-09-16 16:01   ` David Sterba
2020-09-17  8:02     ` Qu Wenruo [this message]
2020-09-17 12:37       ` David Sterba
2020-09-17 13:15         ` Qu Wenruo
2020-09-17 22:41           ` David Sterba
2020-09-17 23:26             ` Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 05/19] btrfs: make btrfs_fs_info::buffer_radix to take sector size devided values Qu Wenruo
2020-09-15  8:27   ` Johannes Thumshirn
2020-09-15 10:04     ` Qu Wenruo
2020-09-15 10:12       ` Johannes Thumshirn
2020-09-15 17:40   ` kernel test robot
2020-09-15 17:40     ` kernel test robot
2020-09-15  5:35 ` [PATCH v2 06/19] btrfs: don't allow tree block to cross page boundary for subpage support Qu Wenruo
2020-09-15  8:37   ` Nikolay Borisov
2020-09-15 10:06     ` Qu Wenruo
2020-09-15  8:44   ` Johannes Thumshirn
2020-09-15  5:35 ` [PATCH v2 07/19] btrfs: update num_extent_pages() to support subpage sized extent buffer Qu Wenruo
2020-09-15  8:42   ` Johannes Thumshirn
2020-09-15 10:07     ` Qu Wenruo
2020-09-15 10:12       ` Johannes Thumshirn
2020-09-15 10:07     ` Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 08/19] btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 09/19] btrfs: make csum_tree_block() handle sectorsize smaller than page size Qu Wenruo
2020-09-15  8:47   ` Johannes Thumshirn
2020-09-15  5:35 ` [PATCH v2 10/19] btrfs: add assert_spin_locked() for attach_extent_buffer_page() Qu Wenruo
2020-09-15  8:52   ` Johannes Thumshirn
2020-09-15  5:35 ` [PATCH v2 11/19] btrfs: extract the extent buffer verification from btree_readpage_end_io_hook() Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 12/19] btrfs: extent_io: only require sector size alignment for page read Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 13/19] btrfs: make btrfs_readpage_end_io_hook() follow sector size Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 14/19] btrfs: make btree inode io_tree has its special owner Qu Wenruo
2020-09-16  9:28   ` Johannes Thumshirn
2020-09-16 16:06   ` David Sterba
2020-09-17  0:02     ` Qu Wenruo
2020-09-17 12:50       ` David Sterba
2020-09-18  8:18         ` Qu Wenruo
2020-09-22 14:06           ` David Sterba
2020-09-22 14:14   ` David Sterba
2020-09-15  5:35 ` [PATCH v2 15/19] btrfs: don't set extent_io_tree bits for btree inode at endio time Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 16/19] btrfs: use extent_io_tree to handle subpage extent buffer allocation Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 17/19] btrfs: implement subpage metadata read and its endio function Qu Wenruo
2020-09-15 18:49   ` kernel test robot
2020-09-16  8:47   ` kernel test robot
2020-09-16  8:47     ` kernel test robot
2020-09-15  5:35 ` [PATCH v2 18/19] btrfs: implement btree_readpage() and try_release_extent_buffer() for subpage Qu Wenruo
2020-09-15  5:35 ` [PATCH v2 19/19] btrfs: allow RO mount of 4K sector size fs on 64K page system Qu Wenruo
2020-09-16  1:35 ` [PATCH v2 00/19] btrfs: add read-only support for subpage sector size Qu Wenruo
2020-09-16 16:18 ` Neal Gompa
2020-09-17  0:03   ` Qu Wenruo
2020-09-17  0:13     ` Neal Gompa
2020-09-17  0:24       ` Qu Wenruo

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