Hi Gu,
> -----Original Message-----
> From: Gu Zheng [mailto:guz.f...@cn.fujitsu.com]
> Sent: Wednesday, November 20, 2013 5:38 PM
> To: Chao Yu
> Cc: '???'; linux-fsde...@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-f2fs-de...@lists.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,
> On 11/20/2013 01:37 PM, Chao Yu wrote:
>
> > Hi Gu,
> >
> >> -----Original Message-----
> >> From: Gu Zheng [mailto:guz.f...@cn.fujitsu.com]
> >> Sent: Monday, November 18, 2013 7:16 PM
> >> To: Chao Yu
> >> Cc: '???'; linux-fsde...@vger.kernel.org; linux-kernel@vger.kernel.org;
> >> linux-f2fs-de...@lists.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...@samsung.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.
Right, I mean that if we want to set first position in bitmap,
we cloud use f2fs_set_bit(0, bitmap) or set_bit(7, bitmap).
Two types of interface could not be used mixedly.
So could we use {set,test,clear}_bit intead of f2fs_{set,test,clear}_bit?
> On the other side, why not introduce a 'f2fs_find_next_bit' if it's
> seriously needed?:)
Agreed, that's a good point, they were really needed for
uniform style and readability.
>
> 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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