On 2017/2/17 10:54, Jaegeuk Kim wrote: > On 02/17, Hou Pengyang wrote: >> On 2017/2/17 7:48, Jaegeuk Kim wrote: >>> Hi Pengyang, >>> >>> Nice >> Hi Jaegeuk, >> catch! >>> >>> I think fggc_threshold needs to be revised, and we need to consider about >>> general victim selection as well. >>> >>> Could you take a look at this? >>> >>>> From 23b265f5ca6405032d092e240c94a827f743e42b Mon Sep 17 00:00:00 2001 >>> From: Hou Pengyang <houpengy...@huawei.com> >>> Date: Thu, 16 Feb 2017 12:34:31 +0000 >>> Subject: [PATCH] f2fs: add ovp valid_blocks check for bg gc victim to fg_gc >>> >>> For foreground gc, greedy algorithm should be adapted, which makes >>> this formula work well: >>> >>> (2 * (100 / config.overprovision + 1) + 6) >>> >>> But currently, we fg_gc have a prior to select bg_gc victim segments to gc >>> first, >>> these victims are selected by cost-benefit algorithm, we can't guarantee >>> such segments >>> have the small valid blocks, which may destroy the f2fs rule, on the >>> worstest case, would >>> consume all the free segments. >>> >>> This patch fix this by add a filter in check_bg_victims, if segment's has # >>> of valid blocks >>> over overprovision ratio, skip such segments. >>> >>> Cc: <sta...@vger.kernel.org> >>> Signed-off-by: Hou Pengyang <houpengy...@huawei.com> >>> Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org> >>> --- >>> fs/f2fs/f2fs.h | 3 +++ >>> fs/f2fs/gc.c | 22 ++++++++++++++++++++-- >>> fs/f2fs/segment.h | 9 +++++++++ >>> 3 files changed, 32 insertions(+), 2 deletions(-) >>> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>> index cc22dc458896..1c9f0cc8f027 100644 >>> --- a/fs/f2fs/f2fs.h >>> +++ b/fs/f2fs/f2fs.h >>> @@ -888,6 +888,9 @@ struct f2fs_sb_info { >>> struct f2fs_gc_kthread *gc_thread; /* GC thread */ >>> unsigned int cur_victim_sec; /* current victim section num */ >>> >>> + /* threshold for converting bg victims for fg */ >>> + u64 fggc_threshold; >>> + >>> /* maximum # of trials to find a victim segment for SSR and GC */ >>> unsigned int max_victim_search; >>> >>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>> index 88e5e7b10ab6..fd4e479820e6 100644 >>> --- a/fs/f2fs/gc.c >>> +++ b/fs/f2fs/gc.c >>> @@ -166,7 +166,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int >>> gc_type, >>> p->ofs_unit = sbi->segs_per_sec; >>> } >>> >>> - if (p->max_search > sbi->max_victim_search) >>> + /* we need to check every dirty segments in the FG_GC case */ >>> + if (gc_type != FG_GC && p->max_search > sbi->max_victim_search) >>> p->max_search = sbi->max_victim_search; >>> >>> p->offset = sbi->last_victim[p->gc_mode]; >>> @@ -199,6 +200,10 @@ static unsigned int check_bg_victims(struct >>> f2fs_sb_info *sbi) >>> for_each_set_bit(secno, dirty_i->victim_secmap, MAIN_SECS(sbi)) { >>> if (sec_usage_check(sbi, secno)) >>> continue; >>> + >>> + if (no_fggc_candidate(sbi, secno)) >>> + continue; >>> + >>> clear_bit(secno, dirty_i->victim_secmap); >>> return secno * sbi->segs_per_sec; >>> } >>> @@ -322,13 +327,15 @@ static int get_victim_by_default(struct f2fs_sb_info >>> *sbi, >>> nsearched++; >>> } >>> >>> - >>> secno = GET_SECNO(sbi, segno); >>> >>> if (sec_usage_check(sbi, secno)) >>> goto next; >>> if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap)) >>> goto next; >>> + if (gc_type == FG_GC && p.alloc_mode == LFS && >>> + no_fggc_candidate(sbi, secno)) >>> + goto next; >>> >>> cost = get_gc_cost(sbi, segno, &p); >>> >>> @@ -989,5 +996,16 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool >>> background) >>> >>> void build_gc_manager(struct f2fs_sb_info *sbi) >>> { >>> + u64 user_block_count, ovp_count, blocks_per_sec, th; >>> + >>> DIRTY_I(sbi)->v_ops = &default_v_ops; >>> + >>> + /* threshold of # of valid blocks in a section for victims of FG_GC */ >>> + user_block_count = sbi->user_block_count; >>> + ovp_count = SM_I(sbi)->ovp_segments << sbi->log_blocks_per_seg; >> >> About the ovp_count calculation, >> >> in mkfs.f2fs, we get ovp_segment by >> >> set_cp(overprov_segment_count, (get_sb(segment_count_main) - >> get_cp(rsvd_segment_count)) * >> config.overprovision / 100); >> >> set_cp(overprov_segment_count, get_cp(overprov_segment_count) + >> get_cp(rsvd_segment_count)); >> >> where the overprov calculation is based on the space excluding the >> rsvd segment, and the final overprov_segment is sum of the REAL >> overprov segments and the rsvd ones. >> >> So, when to calculate the overprov ratio, the rsvd segments should >> be subtracted from the ckpt->overprov_semgents? > > I just got calculation from fresh mounted image. What I could confirm was that > user can see (main_segments - ovp_segments).
I add some log into mkfs.f2fs, and get the config.overprovision, rsvd/ovrp segments, user_block_count, and use the mkfs.f2fs to formatting a 512M disk, where: config.overprovision: 10 ovrp : 50 segments(25600 blocks) rsvd : 28 segments(14336 blocks) user_block_count: 101376 blocks Use ovrp/rsvd/user_block_count to get the ovrp ratio info reversely : 1) user_block_count/(user_block_count + ovrp blocks) 101376/(101376+25600) = 79% 2) user_block_count/(user_block_count + ovrp_blocks - rsvd_blocks) 101376/(101376+25600-14336) = 90% = 1-10% By 2), 1-90%, we can get the original config.overprovion when mkfs.f2fs So I think we should use 2) to calculate ovrp ratio. Anything I miss in 2)? Thanks, > BTW, it's worth to verify reserved_segments with that. > >> >> Thanks, >> >>> + blocks_per_sec = sbi->blocks_per_seg * sbi->segs_per_sec; >>> + >>> + th = user_block_count * 100 * blocks_per_sec / >>> + ((user_block_count + ovp_count) * 100); >>> + sbi->fggc_threshold = th; >>> } >>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h >>> index 5cb5755c75d9..f4020f141d83 100644 >>> --- a/fs/f2fs/segment.h >>> +++ b/fs/f2fs/segment.h >>> @@ -716,6 +716,15 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info >>> *sbi, int base, int type) >>> - (base + 1) + type; >>> } >>> >>> +static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi, >>> + unsigned int secno) >>> +{ >>> + if (get_valid_blocks(sbi, secno, sbi->segs_per_sec) >= >>> + sbi->fggc_threshold) >>> + return true; >>> + return false; >>> +} >>> + >>> static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned >>> int secno) >>> { >>> if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno)) >>> >> > > . > ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel