ext4: add mballoc stats proc file

Add new stats for measuring the performance of mballoc. This patch is
forked from Artem Blagodarenko's work that can be found here:

https://github.com/lustre/lustre-release/blob/master/ldiskfs/kernel_patches/patches/rhel8/ext4-simple-blockalloc.patch

This patch reorganizes the stats by cr level. This is how the output
looks like:

mballoc:
	reqs: 0
	success: 0
	groups_scanned: 0
	cr0_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr1_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr2_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	cr3_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	extents_scanned: 0
		goal_hits: 0
		2^n_hits: 0
		breaks: 0
		lost: 0
	buddies_generated: 0/40
	buddies_time_used: 0
	preallocated: 0
	discarded: 0

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20210401172129.189766-4-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 7ba90a9..67a675d 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1550,9 +1550,13 @@ struct ext4_sb_info {
        atomic_t s_bal_success; /* we found long enough chunks */
        atomic_t s_bal_allocated;       /* in blocks */
        atomic_t s_bal_ex_scanned;      /* total extents scanned */
+       atomic_t s_bal_groups_scanned;  /* number of groups scanned */
        atomic_t s_bal_goals;   /* goal hits */
        atomic_t s_bal_breaks;  /* too long searches */
        atomic_t s_bal_2orders; /* 2^order hits */
+       atomic64_t s_bal_cX_groups_considered[4];
+       atomic64_t s_bal_cX_hits[4];
+       atomic64_t s_bal_cX_failed[4];          /* cX loop didn't find blocks */
        atomic_t s_mb_buddies_generated;        /* number of buddies generated */
        atomic64_t s_mb_generation_time;
        atomic_t s_mb_lost_chunks;
@@ -2856,6 +2860,7 @@ int __init ext4_fc_init_dentry_cache(void);
 extern const struct seq_operations ext4_mb_seq_groups_ops;
 extern long ext4_mb_stats;
 extern long ext4_mb_max_to_scan;
+extern int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset);
 extern int ext4_mb_init(struct super_block *);
 extern int ext4_mb_release(struct super_block *);
 extern ext4_fsblk_t ext4_mb_new_blocks(handle_t *,

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 34ddce5..70b8ab1 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2146,6 +2146,8 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
        ext4_grpblk_t free;
        int ret = 0;
 
+       if (sbi->s_mb_stats)
+               atomic64_inc(&sbi->s_bal_cX_groups_considered[ac->ac_criteria]);
        if (should_lock)
                ext4_lock_group(sb, group);
        free = grp->bb_free;
@@ -2420,6 +2422,9 @@ repeat:
                        if (ac->ac_status != AC_STATUS_CONTINUE)
                                break;
                }
+               /* Processed all groups and haven't found blocks */
+               if (sbi->s_mb_stats && i == ngroups)
+                       atomic64_inc(&sbi->s_bal_cX_failed[cr]);
        }
 
        if (ac->ac_b_ex.fe_len > 0 && ac->ac_status != AC_STATUS_FOUND &&
@@ -2449,6 +2454,9 @@ repeat:
                        goto repeat;
                }
        }
+
+       if (sbi->s_mb_stats && ac->ac_status == AC_STATUS_FOUND)
+               atomic64_inc(&sbi->s_bal_cX_hits[ac->ac_criteria]);
 out:
        if (!err && ac->ac_status != AC_STATUS_FOUND && first_err)
                err = first_err;
@@ -2548,6 +2556,67 @@ const struct seq_operations ext4_mb_seq_groups_ops = {
        .show   = ext4_mb_seq_groups_show,
 };
 
+int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset)
+{
+       struct super_block *sb = (struct super_block *)seq->private;
+       struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+       seq_puts(seq, "mballoc:\n");
+       if (!sbi->s_mb_stats) {
+               seq_puts(seq, "\tmb stats collection turned off.\n");
+               seq_puts(seq, "\tTo enable, please write \"1\" to sysfs file mb_stats.\n");
+               return 0;
+       }
+       seq_printf(seq, "\treqs: %u\n", atomic_read(&sbi->s_bal_reqs));
+       seq_printf(seq, "\tsuccess: %u\n", atomic_read(&sbi->s_bal_success));
+
+       seq_printf(seq, "\tgroups_scanned: %u\n",  atomic_read(&sbi->s_bal_groups_scanned));
+
+       seq_puts(seq, "\tcr0_stats:\n");
+       seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[0]));
+       seq_printf(seq, "\t\tgroups_considered: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_groups_considered[0]));
+       seq_printf(seq, "\t\tuseless_loops: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_failed[0]));
+
+       seq_puts(seq, "\tcr1_stats:\n");
+       seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[1]));
+       seq_printf(seq, "\t\tgroups_considered: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_groups_considered[1]));
+       seq_printf(seq, "\t\tuseless_loops: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_failed[1]));
+
+       seq_puts(seq, "\tcr2_stats:\n");
+       seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[2]));
+       seq_printf(seq, "\t\tgroups_considered: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_groups_considered[2]));
+       seq_printf(seq, "\t\tuseless_loops: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_failed[2]));
+
+       seq_puts(seq, "\tcr3_stats:\n");
+       seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[3]));
+       seq_printf(seq, "\t\tgroups_considered: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_groups_considered[3]));
+       seq_printf(seq, "\t\tuseless_loops: %llu\n",
+                  atomic64_read(&sbi->s_bal_cX_failed[3]));
+       seq_printf(seq, "\textents_scanned: %u\n", atomic_read(&sbi->s_bal_ex_scanned));
+       seq_printf(seq, "\t\tgoal_hits: %u\n", atomic_read(&sbi->s_bal_goals));
+       seq_printf(seq, "\t\t2^n_hits: %u\n", atomic_read(&sbi->s_bal_2orders));
+       seq_printf(seq, "\t\tbreaks: %u\n", atomic_read(&sbi->s_bal_breaks));
+       seq_printf(seq, "\t\tlost: %u\n", atomic_read(&sbi->s_mb_lost_chunks));
+
+       seq_printf(seq, "\tbuddies_generated: %u/%u\n",
+                  atomic_read(&sbi->s_mb_buddies_generated),
+                  ext4_get_groups_count(sb));
+       seq_printf(seq, "\tbuddies_time_used: %llu\n",
+                  atomic64_read(&sbi->s_mb_generation_time));
+       seq_printf(seq, "\tpreallocated: %u\n",
+                  atomic_read(&sbi->s_mb_preallocated));
+       seq_printf(seq, "\tdiscarded: %u\n",
+                  atomic_read(&sbi->s_mb_discarded));
+       return 0;
+}
+
 static struct kmem_cache *get_groupinfo_cache(int blocksize_bits)
 {
        int cache_index = blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE;
@@ -2975,9 +3044,10 @@ int ext4_mb_release(struct super_block *sb)
                                atomic_read(&sbi->s_bal_reqs),
                                atomic_read(&sbi->s_bal_success));
                ext4_msg(sb, KERN_INFO,
-                     "mballoc: %u extents scanned, %u goal hits, "
+                     "mballoc: %u extents scanned, %u groups scanned, %u goal hits, "
                                "%u 2^N hits, %u breaks, %u lost",
                                atomic_read(&sbi->s_bal_ex_scanned),
+                               atomic_read(&sbi->s_bal_groups_scanned),
                                atomic_read(&sbi->s_bal_goals),
                                atomic_read(&sbi->s_bal_2orders),
                                atomic_read(&sbi->s_bal_breaks),
@@ -3580,12 +3650,13 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
 {
        struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
 
-       if (sbi->s_mb_stats && ac->ac_g_ex.fe_len > 1) {
+       if (sbi->s_mb_stats && ac->ac_g_ex.fe_len >= 1) {
                atomic_inc(&sbi->s_bal_reqs);
                atomic_add(ac->ac_b_ex.fe_len, &sbi->s_bal_allocated);
                if (ac->ac_b_ex.fe_len >= ac->ac_o_ex.fe_len)
                        atomic_inc(&sbi->s_bal_success);
                atomic_add(ac->ac_found, &sbi->s_bal_ex_scanned);
+               atomic_add(ac->ac_groups_scanned, &sbi->s_bal_groups_scanned);
                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);

diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 7367ba4..1b5580e 100644 (file)
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -530,6 +530,8 @@ int ext4_register_sysfs(struct super_block *sb)
                                        ext4_fc_info_show, sb);
                proc_create_seq_data("mb_groups", S_IRUGO, sbi->s_proc,
                                &ext4_mb_seq_groups_ops, sb);
+               proc_create_single_data("mb_stats", 0444, sbi->s_proc,
+                               ext4_seq_mb_stats_show, sb);
        }
        return 0;
 }