From 7e170922f06bf46effa7c57f6035fc463d6edc7e Mon Sep 17 00:00:00 2001 From: Ojaswin Mujoo Date: Tue, 30 May 2023 18:03:49 +0530 Subject: [PATCH] ext4: Add allocation criteria 1.5 (CR1_5) CR1_5 aims to optimize allocations which can't be satisfied in CR1. The fact that we couldn't find a group in CR1 suggests that it would be difficult to find a continuous extent to compleltely satisfy our allocations. So before falling to the slower CR2, in CR1.5 we proactively trim the the preallocations so we can find a group with (free / fragments) big enough. This speeds up our allocation at the cost of slightly reduced preallocation. The patch also adds a new sysfs tunable: * /sys/fs/ext4//mb_cr1_5_max_trim_order This controls how much CR1.5 can trim a request before falling to CR2. For example, for a request of order 7 and max trim order 2, CR1.5 can trim this upto order 5. Suggested-by: Ritesh Harjani (IBM) Signed-off-by: Ojaswin Mujoo Reviewed-by: Ritesh Harjani (IBM) Link: https://lore.kernel.org/r/150fdf65c8e4cc4dba71e020ce0859bcf636a5ff.1685449706.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o --- fs/ext4/ext4.h | 8 ++- fs/ext4/mballoc.c | 135 +++++++++++++++++++++++++++++++++--- fs/ext4/mballoc.h | 13 ++++ fs/ext4/sysfs.c | 2 + include/trace/events/ext4.h | 2 + 5 files changed, 150 insertions(+), 10 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index e4f53947f51f..fb9d2e2a9e42 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -133,13 +133,14 @@ enum SHIFT_DIRECTION { * criteria the slower the allocation. We start at lower criterias and keep * falling back to higher ones if we are not able to find any blocks. */ -#define EXT4_MB_NUM_CRS 4 +#define EXT4_MB_NUM_CRS 5 /* * All possible allocation criterias for mballoc */ enum criteria { CR0, CR1, + CR1_5, CR2, CR3, }; @@ -185,6 +186,9 @@ enum criteria { #define EXT4_MB_CR0_OPTIMIZED 0x8000 /* Avg fragment size rb tree lookup succeeded at least once for cr = 1 */ #define EXT4_MB_CR1_OPTIMIZED 0x00010000 +/* Avg fragment size rb tree lookup succeeded at least once for cr = 1.5 */ +#define EXT4_MB_CR1_5_OPTIMIZED 0x00020000 + struct ext4_allocation_request { /* target inode for block we're allocating */ struct inode *inode; @@ -1549,6 +1553,7 @@ struct ext4_sb_info { unsigned long s_mb_last_start; unsigned int s_mb_prefetch; unsigned int s_mb_prefetch_limit; + unsigned int s_mb_cr1_5_max_trim_order; /* stats for buddy allocator */ atomic_t s_bal_reqs; /* number of reqs with len > 1 */ @@ -1563,6 +1568,7 @@ struct ext4_sb_info { atomic_t s_bal_2orders; /* 2^order hits */ atomic_t s_bal_cr0_bad_suggestions; atomic_t s_bal_cr1_bad_suggestions; + atomic_t s_bal_cr1_5_bad_suggestions; atomic64_t s_bal_cX_groups_considered[EXT4_MB_NUM_CRS]; atomic64_t s_bal_cX_hits[EXT4_MB_NUM_CRS]; atomic64_t s_bal_cX_failed[EXT4_MB_NUM_CRS]; /* cX loop didn't find blocks */ diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 7fc99b209546..cc9ad7469fbb 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -165,6 +165,14 @@ * equal to request size using our average fragment size group lists (data * structure 2) in O(1) time. * + * At CR1.5 (aka CR1_5), we aim to optimize allocations which can't be satisfied + * in CR1. The fact that we couldn't find a group in CR1 suggests that there is + * no BG that has average fragment size > goal length. So before falling to the + * slower CR2, in CR1.5 we proactively trim goal length and then use the same + * fragment lists as CR1 to find a BG with a big enough average fragment size. + * This increases the chances of finding a suitable block group in O(1) time and + * results * in faster allocation at the cost of reduced size of allocation. + * * If "mb_optimize_scan" mount option is not set, mballoc traverses groups in * linear order which requires O(N) search time for each CR0 and CR1 phase. * @@ -962,6 +970,91 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac, *group = grp->bb_group; ac->ac_flags |= EXT4_MB_CR1_OPTIMIZED; } else { + *new_cr = CR1_5; + } +} + +/* + * We couldn't find a group in CR1 so try to find the highest free fragment + * order we have and proactively trim the goal request length to that order to + * find a suitable group faster. + * + * This optimizes allocation speed at the cost of slightly reduced + * preallocations. However, we make sure that we don't trim the request too + * much and fall to CR2 in that case. + */ +static void ext4_mb_choose_next_group_cr1_5(struct ext4_allocation_context *ac, + enum criteria *new_cr, ext4_group_t *group, ext4_group_t ngroups) +{ + struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb); + struct ext4_group_info *grp = NULL; + int i, order, min_order; + unsigned long num_stripe_clusters = 0; + + if (unlikely(ac->ac_flags & EXT4_MB_CR1_5_OPTIMIZED)) { + if (sbi->s_mb_stats) + atomic_inc(&sbi->s_bal_cr1_5_bad_suggestions); + } + + /* + * mb_avg_fragment_size_order() returns order in a way that makes + * retrieving back the length using (1 << order) inaccurate. Hence, use + * fls() instead since we need to know the actual length while modifying + * goal length. + */ + order = fls(ac->ac_g_ex.fe_len); + min_order = order - sbi->s_mb_cr1_5_max_trim_order; + if (min_order < 0) + min_order = 0; + + if (1 << min_order < ac->ac_o_ex.fe_len) + min_order = fls(ac->ac_o_ex.fe_len) + 1; + + if (sbi->s_stripe > 0) { + /* + * We are assuming that stripe size is always a multiple of + * cluster ratio otherwise __ext4_fill_super exists early. + */ + num_stripe_clusters = EXT4_NUM_B2C(sbi, sbi->s_stripe); + if (1 << min_order < num_stripe_clusters) + min_order = fls(num_stripe_clusters); + } + + for (i = order; i >= min_order; i--) { + int frag_order; + /* + * Scale down goal len to make sure we find something + * in the free fragments list. Basically, reduce + * preallocations. + */ + ac->ac_g_ex.fe_len = 1 << i; + + if (num_stripe_clusters > 0) { + /* + * Try to round up the adjusted goal to stripe size + * (in cluster units) multiple for efficiency. + * + * XXX: Is s->stripe always a power of 2? In that case + * we can use the faster round_up() variant. + */ + ac->ac_g_ex.fe_len = roundup(ac->ac_g_ex.fe_len, + num_stripe_clusters); + } + + frag_order = mb_avg_fragment_size_order(ac->ac_sb, + ac->ac_g_ex.fe_len); + + grp = ext4_mb_find_good_group_avg_frag_lists(ac, frag_order); + if (grp) + break; + } + + if (grp) { + *group = grp->bb_group; + ac->ac_flags |= EXT4_MB_CR1_5_OPTIMIZED; + } else { + /* Reset goal length to original goal length before falling into CR2 */ + ac->ac_g_ex.fe_len = ac->ac_orig_goal_len; *new_cr = CR2; } } @@ -1028,6 +1121,8 @@ static void ext4_mb_choose_next_group(struct ext4_allocation_context *ac, ext4_mb_choose_next_group_cr0(ac, new_cr, group, ngroups); } else if (*new_cr == CR1) { ext4_mb_choose_next_group_cr1(ac, new_cr, group, ngroups); + } else if (*new_cr == CR1_5) { + ext4_mb_choose_next_group_cr1_5(ac, new_cr, group, ngroups); } else { /* * TODO: For CR=2, we can arrange groups in an rb tree sorted by @@ -2351,7 +2446,7 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac, if (ac->ac_criteria < CR2) { /* - * In CR1, we are sure that this group will + * In CR1 and CR1_5, we are sure that this group will * have a large enough continuous free extent, so skip * over the smaller free extents */ @@ -2483,6 +2578,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac, return true; case CR1: + case CR1_5: if ((free / fragments) >= ac->ac_g_ex.fe_len) return true; break; @@ -2747,7 +2843,7 @@ repeat: * spend a lot of time loading imperfect groups */ if ((prefetch_grp == group) && - (cr > CR1 || + (cr > CR1_5 || prefetch_ios < sbi->s_mb_prefetch_limit)) { nr = sbi->s_mb_prefetch; if (ext4_has_feature_flex_bg(sb)) { @@ -2787,7 +2883,7 @@ repeat: ac->ac_groups_scanned++; if (cr == CR0) ext4_mb_simple_scan_group(ac, &e4b); - else if (cr == CR1 && sbi->s_stripe && + else if ((cr == CR1 || cr == CR1_5) && sbi->s_stripe && !(ac->ac_g_ex.fe_len % EXT4_B2C(sbi, sbi->s_stripe))) ext4_mb_scan_aligned(ac, &e4b); @@ -2803,6 +2899,11 @@ repeat: /* Processed all groups and haven't found blocks */ if (sbi->s_mb_stats && i == ngroups) atomic64_inc(&sbi->s_bal_cX_failed[cr]); + + if (i == ngroups && ac->ac_criteria == CR1_5) + /* Reset goal length to original goal length before + * falling into CR2 */ + ac->ac_g_ex.fe_len = ac->ac_orig_goal_len; } if (ac->ac_b_ex.fe_len > 0 && ac->ac_status != AC_STATUS_FOUND && @@ -2972,6 +3073,16 @@ int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset) seq_printf(seq, "\t\tbad_suggestions: %u\n", atomic_read(&sbi->s_bal_cr1_bad_suggestions)); + seq_puts(seq, "\tcr1.5_stats:\n"); + seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR1_5])); + seq_printf(seq, "\t\tgroups_considered: %llu\n", + atomic64_read(&sbi->s_bal_cX_groups_considered[CR1_5])); + seq_printf(seq, "\t\textents_scanned: %u\n", atomic_read(&sbi->s_bal_cX_ex_scanned[CR1_5])); + seq_printf(seq, "\t\tuseless_loops: %llu\n", + atomic64_read(&sbi->s_bal_cX_failed[CR1_5])); + seq_printf(seq, "\t\tbad_suggestions: %u\n", + atomic_read(&sbi->s_bal_cr1_5_bad_suggestions)); + seq_puts(seq, "\tcr2_stats:\n"); seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR2])); seq_printf(seq, "\t\tgroups_considered: %llu\n", @@ -3489,6 +3600,8 @@ int ext4_mb_init(struct super_block *sb) sbi->s_mb_stats = MB_DEFAULT_STATS; sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD; sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS; + sbi->s_mb_cr1_5_max_trim_order = MB_DEFAULT_CR1_5_TRIM_ORDER; + /* * The default group preallocation is 512, which for 4k block * sizes translates to 2 megabytes. However for bigalloc file @@ -4392,6 +4505,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, * placement or satisfy big request as is */ ac->ac_g_ex.fe_logical = start; ac->ac_g_ex.fe_len = EXT4_NUM_B2C(sbi, size); + ac->ac_orig_goal_len = ac->ac_g_ex.fe_len; /* define goal start in order to merge */ if (ar->pright && (ar->lright == (start + size)) && @@ -4435,8 +4549,10 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac) if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start && ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group) atomic_inc(&sbi->s_bal_goals); - if (ac->ac_f_ex.fe_len == ac->ac_g_ex.fe_len) + /* did we allocate as much as normalizer originally wanted? */ + if (ac->ac_f_ex.fe_len == ac->ac_orig_goal_len) atomic_inc(&sbi->s_bal_len_goals); + if (ac->ac_found > sbi->s_mb_max_to_scan) atomic_inc(&sbi->s_bal_breaks); } @@ -4921,7 +5037,7 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) pa = ac->ac_pa; - if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) { + if (ac->ac_b_ex.fe_len < ac->ac_orig_goal_len) { int new_bex_start; int new_bex_end; @@ -4936,14 +5052,14 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) * fragmentation in check while ensuring logical range of best * extent doesn't overflow out of goal extent: * - * 1. Check if best ex can be kept at end of goal and still - * cover original start + * 1. Check if best ex can be kept at end of goal (before + * cr_best_avail trimmed it) and still cover original start * 2. Else, check if best ex can be kept at start of goal and * still cover original start * 3. Else, keep the best ex at start of original request. */ new_bex_end = ac->ac_g_ex.fe_logical + - EXT4_C2B(sbi, ac->ac_g_ex.fe_len); + EXT4_C2B(sbi, ac->ac_orig_goal_len); new_bex_start = new_bex_end - EXT4_C2B(sbi, ac->ac_b_ex.fe_len); if (ac->ac_o_ex.fe_logical >= new_bex_start) goto adjust_bex; @@ -4964,7 +5080,7 @@ adjust_bex: BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical); BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len); BUG_ON(new_bex_end > (ac->ac_g_ex.fe_logical + - EXT4_C2B(sbi, ac->ac_g_ex.fe_len))); + EXT4_C2B(sbi, ac->ac_orig_goal_len))); } pa->pa_lstart = ac->ac_b_ex.fe_logical; @@ -5584,6 +5700,7 @@ ext4_mb_initialize_context(struct ext4_allocation_context *ac, ac->ac_o_ex.fe_start = block; ac->ac_o_ex.fe_len = len; ac->ac_g_ex = ac->ac_o_ex; + ac->ac_orig_goal_len = ac->ac_g_ex.fe_len; ac->ac_flags = ar->flags; /* we have to define context: we'll work with a file or diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h index acfdc204e15d..bddc0335c261 100644 --- a/fs/ext4/mballoc.h +++ b/fs/ext4/mballoc.h @@ -85,6 +85,13 @@ */ #define MB_DEFAULT_LINEAR_SCAN_THRESHOLD 16 +/* + * The maximum order upto which CR1.5 can trim a particular allocation request. + * Example, if we have an order 7 request and max trim order of 3, CR1.5 can + * trim this upto order 4. + */ +#define MB_DEFAULT_CR1_5_TRIM_ORDER 3 + /* * Number of valid buddy orders */ @@ -179,6 +186,12 @@ struct ext4_allocation_context { /* copy of the best found extent taken before preallocation efforts */ struct ext4_free_extent ac_f_ex; + /* + * goal len can change in CR1.5, so save the original len. This is + * used while adjusting the PA window and for accounting. + */ + ext4_grpblk_t ac_orig_goal_len; + __u32 ac_groups_considered; __u32 ac_flags; /* allocation hints */ __u16 ac_groups_scanned; diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index 3042bc605bbf..4a5c08c8dddb 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -223,6 +223,7 @@ EXT4_RW_ATTR_SBI_UI(warning_ratelimit_interval_ms, s_warning_ratelimit_state.int EXT4_RW_ATTR_SBI_UI(warning_ratelimit_burst, s_warning_ratelimit_state.burst); EXT4_RW_ATTR_SBI_UI(msg_ratelimit_interval_ms, s_msg_ratelimit_state.interval); EXT4_RW_ATTR_SBI_UI(msg_ratelimit_burst, s_msg_ratelimit_state.burst); +EXT4_RW_ATTR_SBI_UI(mb_cr1_5_max_trim_order, s_mb_cr1_5_max_trim_order); #ifdef CONFIG_EXT4_DEBUG EXT4_RW_ATTR_SBI_UL(simulate_fail, s_simulate_fail); #endif @@ -273,6 +274,7 @@ static struct attribute *ext4_attrs[] = { ATTR_LIST(warning_ratelimit_burst), ATTR_LIST(msg_ratelimit_interval_ms), ATTR_LIST(msg_ratelimit_burst), + ATTR_LIST(mb_cr1_5_max_trim_order), ATTR_LIST(errors_count), ATTR_LIST(warning_count), ATTR_LIST(msg_count), diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h index 51eab82e897c..2a3ffa081d2c 100644 --- a/include/trace/events/ext4.h +++ b/include/trace/events/ext4.h @@ -122,6 +122,7 @@ TRACE_DEFINE_ENUM(EXT4_FC_REASON_MAX); TRACE_DEFINE_ENUM(CR0); TRACE_DEFINE_ENUM(CR1); +TRACE_DEFINE_ENUM(CR1_5); TRACE_DEFINE_ENUM(CR2); TRACE_DEFINE_ENUM(CR3); @@ -129,6 +130,7 @@ TRACE_DEFINE_ENUM(CR3); __print_symbolic(cr, \ { CR0, "CR0" }, \ { CR1, "CR1" }, \ + { CR1_5, "CR1.5" } \ { CR2, "CR2" }, \ { CR3, "CR3" })