Re: [f2fs-dev] [PATCH V2 2/2] f2fs: read contiguous sit entry pagesby merging for mount performance

[Gu Zheng]

Hi Yu,
On 11/20/2013 01:37 PM, Chao Yu wrote:

> Hi Gu,
> 
>> -----Original Message-----
>> From: Gu Zheng [mailto:guz.fnst@xxxxxxxxxxxxxx]
>> Sent: Monday, November 18, 2013 7:16 PM
>> To: Chao Yu
>> Cc: '???'; linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx; 谭姝
>> Subject: Re: [f2fs-dev] [PATCH V2 2/2] f2fs: read contiguous sit entry pages by merging for mount performance
>>
>> Hi Yu,
>> One more comment, please refer to inline.
>> On 11/16/2013 02:15 PM, Chao Yu wrote:
>>
>>> Previously we read sit entries page one by one, this method lost the chance of reading contiguous page together.
>>> So we read pages as contiguous as possible for better mount performance.
>>>
>>> v1-->v2:
>>>  o merge judgements/use 'Continue' or 'Break' instead of 'Goto' as Gu Zheng suggested.
>>>  o add mark_page_accessed () before release page to delay VM reclaiming them.
>>>
>>> Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
>>> ---
>>>  fs/f2fs/segment.c |  108 ++++++++++++++++++++++++++++++++++++++++-------------
>>>  fs/f2fs/segment.h |    2 +
>>>  2 files changed, 84 insertions(+), 26 deletions(-)
>>>
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index fa284d3..656fe40 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -14,6 +14,7 @@
>>>  #include <linux/blkdev.h>
>>>  #include <linux/prefetch.h>
>>>  #include <linux/vmalloc.h>
>>> +#include <linux/swap.h>
>>>
>>>  #include "f2fs.h"
>>>  #include "segment.h"
>>> @@ -1480,41 +1481,96 @@ static int build_curseg(struct f2fs_sb_info *sbi)
>>>  	return restore_curseg_summaries(sbi);
>>>  }
>>>
>>> +static int ra_sit_pages(struct f2fs_sb_info *sbi, int start,
>>> +					int nrpages, bool *is_order)
>>> +{
>>> +	struct address_space *mapping = sbi->meta_inode->i_mapping;
>>> +	struct sit_info *sit_i = SIT_I(sbi);
>>> +	struct page *page;
>>> +	block_t blk_addr;
>>> +	int blkno = start, readcnt = 0;
>>> +	int sit_blk_cnt = SIT_BLK_CNT(sbi);
>>> +
>>> +	for (; blkno < start + nrpages && blkno < sit_blk_cnt; blkno++) {
>>> +
>>> +		if ((!f2fs_test_bit(blkno, sit_i->sit_bitmap) ^ !*is_order)) {
>>> +			*is_order = !*is_order;
>>> +			break;
>>> +		}
>>> +
>>> +		blk_addr = sit_i->sit_base_addr + blkno;
>>> +		if (*is_order)
>>> +			blk_addr += sit_i->sit_blocks;
>>> +repeat:
>>> +		page = grab_cache_page(mapping, blk_addr);
>>> +		if (!page) {
>>> +			cond_resched();
>>> +			goto repeat;
>>> +		}
>>> +		if (PageUptodate(page)) {
>>> +			mark_page_accessed(page);
>>> +			f2fs_put_page(page, 1);
>>> +			readcnt++;
>>> +			continue;
>>> +		}
>>> +
>>> +		submit_read_page(sbi, page, blk_addr, READ_SYNC);
>>> +
>>> +		mark_page_accessed(page);
>>> +		f2fs_put_page(page, 0);
>>> +		readcnt++;
>>> +	}
>>> +
>>> +	f2fs_submit_read_bio(sbi, READ_SYNC);
>>> +	return readcnt;
>>> +}
>>> +
>>>  static void build_sit_entries(struct f2fs_sb_info *sbi)
>>>  {
>>>  	struct sit_info *sit_i = SIT_I(sbi);
>>>  	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_COLD_DATA);
>>>  	struct f2fs_summary_block *sum = curseg->sum_blk;
>>> -	unsigned int start;
>>> -
>>> -	for (start = 0; start < TOTAL_SEGS(sbi); start++) {
>>> -		struct seg_entry *se = &sit_i->sentries[start];
>>> -		struct f2fs_sit_block *sit_blk;
>>> -		struct f2fs_sit_entry sit;
>>> -		struct page *page;
>>> -		int i;
>>> +	bool is_order = f2fs_test_bit(0, sit_i->sit_bitmap) ? true : false;
>>> +	int sit_blk_cnt = SIT_BLK_CNT(sbi);
>>> +	unsigned int i, start, end;
>>> +	unsigned int readed, start_blk = 0;
>>>
>>> -		mutex_lock(&curseg->curseg_mutex);
>>> -		for (i = 0; i < sits_in_cursum(sum); i++) {
>>> -			if (le32_to_cpu(segno_in_journal(sum, i)) == start) {
>>> -				sit = sit_in_journal(sum, i);
>>> -				mutex_unlock(&curseg->curseg_mutex);
>>> -				goto got_it;
>>> +	do {
>>
>> How about using find_next_bit to get the suitable start_blk if the next blk
>> is not ordered here? And it also can simplify the logic of ra_sit_pages().
> 
> That's a good idea.
> But I thought there maybe endianness problem between test_bit and 
> f2fs_test_bit, so find_next_bit may get wrong result. Am I right?

IMO, find_next_bit can do well with endianness issue internally, if
it's not so, that may be a weakness.
On the other side, why not introduce a 'f2fs_find_next_bit' if it's
seriously needed?:)

Regards,
Gu

> 
> Thanks,
> Yu
>>
>> Thanks,
>> Gu
>>
>>> +		readed = ra_sit_pages(sbi, start_blk, sit_blk_cnt, &is_order);
>>> +
>>> +		start = start_blk * sit_i->sents_per_block;
>>> +		end = (start_blk + readed) * sit_i->sents_per_block;
>>> +
>>> +		for (; start < end && start < TOTAL_SEGS(sbi); start++) {
>>> +			struct seg_entry *se = &sit_i->sentries[start];
>>> +			struct f2fs_sit_block *sit_blk;
>>> +			struct f2fs_sit_entry sit;
>>> +			struct page *page;
>>> +
>>> +			mutex_lock(&curseg->curseg_mutex);
>>> +			for (i = 0; i < sits_in_cursum(sum); i++) {
>>> +				if (le32_to_cpu(segno_in_journal(sum, i)) == start) {
>>> +					sit = sit_in_journal(sum, i);
>>> +					mutex_unlock(&curseg->curseg_mutex);
>>> +					goto got_it;
>>> +				}
>>>  			}
>>> -		}
>>> -		mutex_unlock(&curseg->curseg_mutex);
>>> -		page = get_current_sit_page(sbi, start);
>>> -		sit_blk = (struct f2fs_sit_block *)page_address(page);
>>> -		sit = sit_blk->entries[SIT_ENTRY_OFFSET(sit_i, start)];
>>> -		f2fs_put_page(page, 1);
>>> +			mutex_unlock(&curseg->curseg_mutex);
>>> +
>>> +			page = get_current_sit_page(sbi, start);
>>> +			sit_blk = (struct f2fs_sit_block *)page_address(page);
>>> +			sit = sit_blk->entries[SIT_ENTRY_OFFSET(sit_i, start)];
>>> +			f2fs_put_page(page, 1);
>>>  got_it:
>>> -		check_block_count(sbi, start, &sit);
>>> -		seg_info_from_raw_sit(se, &sit);
>>> -		if (sbi->segs_per_sec > 1) {
>>> -			struct sec_entry *e = get_sec_entry(sbi, start);
>>> -			e->valid_blocks += se->valid_blocks;
>>> +			check_block_count(sbi, start, &sit);
>>> +			seg_info_from_raw_sit(se, &sit);
>>> +			if (sbi->segs_per_sec > 1) {
>>> +				struct sec_entry *e = get_sec_entry(sbi, start);
>>> +				e->valid_blocks += se->valid_blocks;
>>> +			}
>>>  		}
>>> -	}
>>> +		start_blk += readed;
>>
>>
>>
>>
>>> +	} while (start_blk < sit_blk_cnt);
>>>  }
>>>
>>>  static void init_free_segmap(struct f2fs_sb_info *sbi)
>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>>> index 269f690..ad5b9f1 100644
>>> --- a/fs/f2fs/segment.h
>>> +++ b/fs/f2fs/segment.h
>>> @@ -83,6 +83,8 @@
>>>  	(segno / SIT_ENTRY_PER_BLOCK)
>>>  #define	START_SEGNO(sit_i, segno)		\
>>>  	(SIT_BLOCK_OFFSET(sit_i, segno) * SIT_ENTRY_PER_BLOCK)
>>> +#define SIT_BLK_CNT(sbi)			\
>>> +	((TOTAL_SEGS(sbi) + SIT_ENTRY_PER_BLOCK - 1) / SIT_ENTRY_PER_BLOCK)
>>>  #define f2fs_bitmap_size(nr)			\
>>>  	(BITS_TO_LONGS(nr) * sizeof(unsigned long))
>>>  #define TOTAL_SEGS(sbi)	(SM_I(sbi)->main_segments)
> 
> 
> 


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