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Date: Thu, 14 Nov 2013 18:31:03 +0800
From: Gu Zheng <guz.fnst@...fujitsu.com>
To: Chao Yu <chao2.yu@...sung.com>
CC: "'???'" <jaegeuk.kim@...sung.com>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
'谭姝' <shu.tan@...sung.com>
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: read contiguous sit entry pages
by merging for mount performance
Hi Yu,
On 11/13/2013 04:10 PM, Chao Yu wrote:
> Hi Gu,
>
>> -----Original Message-----
>> From: Gu Zheng [mailto:guz.fnst@...fujitsu.com]
>> Sent: Wednesday, November 13, 2013 11:39 AM
>> To: Chao Yu
>> Cc: ???; linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org; linux-f2fs-devel@...ts.sourceforge.net; 谭姝
>> Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: read contiguous sit entry pages by merging for mount performance
>>
>> Hi Yu,
>> On 11/12/2013 01:18 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.
>>>
>>> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
>>> ---
>>> fs/f2fs/f2fs.h | 2 ++
>>> fs/f2fs/segment.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>>> fs/f2fs/segment.h | 2 ++
>>> 3 files changed, 66 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 0afdcec..bfe9d87 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -1113,6 +1113,8 @@ struct page *find_data_page(struct inode *, pgoff_t, bool);
>>> struct page *get_lock_data_page(struct inode *, pgoff_t);
>>> struct page *get_new_data_page(struct inode *, struct page *, pgoff_t, bool);
>>> int f2fs_readpage(struct f2fs_sb_info *, struct page *, block_t, int);
>>> +void f2fs_submit_read_bio(struct f2fs_sb_info *, int);
>>> +void submit_read_page(struct f2fs_sb_info *, struct page *, block_t, int);
>>
>> Better to move these declarations into PATCH 1/2.
>
> Okay, I will move it to the right place.
>
>>
>>> int do_write_data_page(struct page *);
>>>
>>> /*
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index 86dc289..414c351 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -1474,19 +1474,72 @@ 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, readcnt = 0;
>>> + int sit_blk_cnt = SIT_BLK_CNT(sbi);
>>> +
>>> + for (blkno = start; blkno < start + nrpages; blkno++) {
>>> +
>>> + if (blkno >= sit_blk_cnt)
>>
>> Merge these two judgements:
>> for (blkno = start; blkno < start + nrpages && blkno < sit_blk_cnt; blkno++)
>
> Right, but the line may over 80 characters, if we split this line, it seems not suitable.
> So how about this?
> int blkno = start, readcnt = 0;
> int sit_blk_cnt = SIT_BLK_CNT(sbi);
>
> for (; blkno < start + nrpages && blkno < sit_blk_cnt; blkno++) {
More neat！
>
>>
>>> + goto out;
>>
>>> + if ((!f2fs_test_bit(blkno, sit_i->sit_bitmap) ^ !*is_order)) {
>>> + *is_order = !*is_order;
>>> + goto out;
>>
>> 'Break' seems more suitable.
>
> Yes, you are right.
>
>>
>>> + }
>>> +
>>> + 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)) {
>>> + f2fs_put_page(page, 1);
>>> + readcnt++;
>>> + goto out;
>>
>> Here may be 'Continue'.
>
> 'Out' label could be removed after this modification.
> It seems more neat.
Right.
>
>>
>>> + }
>>> +
>>> + submit_read_page(sbi, page, blk_addr, READ_SYNC);
>>> +
>>> + page_cache_release(page);
>>
>> Put page here seems not a good idea, otherwise all your work may be in vain.
>
> You mean that pages could be reclaimed by VM when out of memory?
> IMO, it is designed more like VM read ahead because we should concern
> memory state of system, and still we have second chance to read these pages.
>
Yes, but we can avoid to read the same page secondly, that's a serious waste, if we still
reread the page in get_current_sit_page(), all the improvement will disappear.
> Could we use mark_page_accessed () to delay VM reclaimed them?
IMO, this is the right way.
>
>>
>>> + readcnt++;
>>> + }
>>> +out:
>>> + 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;
>>> + bool is_order = f2fs_test_bit(0, sit_i->sit_bitmap) ? true : false;
>>> + int sit_blk_cnt = SIT_BLK_CNT(sbi);
>>> + int bio_blocks = MAX_BIO_BLOCKS(max_hw_blocks(sbi));
>>> + unsigned int i, start, end;
>>> + unsigned int readed, start_blk = 0;
>>>
>>> - for (start = 0; start < TOTAL_SEGS(sbi); start++) {
>>> +next:
>>> + readed = ra_sit_pages(sbi, start_blk, bio_blocks, &is_order);
>>
>> In fact, you know how many blocks that you want to read(SIT_BLK_CNT(sbi)),
>> so here sit_blk_cnt is more suitable than a MAX one, and it also can make
>> the logic of ra_sit_pages more simple.
>
> Right.
>
> BTW, I am considering that maybe we should send dynamical cnt which
> depend on memory state of system more than the logic of ra_sit_pages.
> May it's the work of anther patch. How do you think?
Agree. It's the same as the way that I suggested previously, and it can make
the contiguous pages reading api more common.
Regards,
Gu
>
>>
>>> +
>>> + 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;
>>> - int i;
>>>
>>> mutex_lock(&curseg->curseg_mutex);
>>> for (i = 0; i < sits_in_cursum(sum); i++) {
>>> @@ -1497,6 +1550,7 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
>>> }
>>> }
>>> 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)];
>>> @@ -1509,6 +1563,11 @@ got_it:
>>> e->valid_blocks += se->valid_blocks;
>>> }
>>> }
>>> +
>>> + start_blk += readed;
>>> + if (start_blk >= sit_blk_cnt)
>>> + return;
>>> + goto next;
>>
>> Using do {...} while(start_blk < sit_blk_cnt) rather than the so big upstream goto.
>
> Yes, you are right.
>
>>
>>> }
>>>
>>> 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)
>
> Thanks!
>
> Regards,
> Yu
>
>
>
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