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? 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