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Date: Wed, 20 Nov 2013 17:38:16 +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 V2 2/2] f2fs: read contiguous sit entry pages
by merging for mount performance
Hi Yu,
On 11/20/2013 01:37 PM, Chao Yu wrote:
> Hi Gu,
>
>> -----Original Message-----
>> From: Gu Zheng [mailto:guz.fnst@...fujitsu.com]
>> Sent: Monday, November 18, 2013 7:16 PM
>> 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 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@...sung.com>
>>> ---
>>> 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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