Thanks Artem for pointing that out. The reason I added s_bal_groups_considered inside ext4_mb_good_group() was that, in the next patches in the series, the new allocator structures call ext4_mb_good_group() before to check if the group looked up using cr0 lists or cr 1 tree is good or not. Having this counter incremented in ext4_mb_good_group() helps us measure the overhead of the new structures too. I'd like to keep that. But you're right, even without those optimizations, ext4_mb_good_group() gets called twice. Which means, with these optimizations it will get called 3 times. So, perhaps we can increment s_bal_groups_considered in ext4_mb_good_group_nolock() as you mentioned, and then we can also increment it in the following patches just before calling ext4_mb_good_group(). I'll note that for the next version, thanks! - Harshad On Fri, Feb 12, 2021 at 8:52 AM Благодаренко Артём <artem.blagodarenko@xxxxxxxxx> wrote: > > Hello Harshad, > > Thanks for this great work. I am still testing these patches. Right now I have noticed this flow - > s_bal_groups_considered is counted twice. It is placed to ext4_mb_good_group, that is called twice, > one time from ext4_mb_good_group_nolock and again from ext4_mb_good_group_nolock. > I’d rather put s_bal_groups_considered into the ext4_mb_good_group_nolock(). > > Here is simple execution (on non-fragmented partition) with old counter location > > [root@CO82 ~]# dd if=/dev/zero of=/mnt/file4 bs=2M count=2 conv=fsync > 2+0 records in > 2+0 records out > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.0137407 s, 305 MB/s > [root@CO82 ~]# cat /proc/fs/ext4/sda2/mb_stats > mballoc: > reqs: 2 > success: 1 > groups_scanned: 2 > groups_considered: 4 > extents_scanned: 2 > goal_hits: 0 > 2^n_hits: 2 > breaks: 0 > lost: 0 > useless_c0_loops: 0 > useless_c1_loops: 0 > useless_c2_loops: 0 > useless_c3_loops: 0 > buddies_generated: 60/969 > buddies_time_used: 9178136 > preallocated: 5612 > discarded: 0 > [root@CO82 ~]# > > And location that suggested > [root@CO82 ~]# dd if=/dev/zero of=/mnt/file3 bs=2M count=2 conv=fsync > 2+0 records in > 2+0 records out > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.0155074 s, 270 MB/s > [root@CO82 ~]# cat /proc/fs/ext4/sda2/mb_stats > mballoc: > reqs: 3 > success: 2 > groups_scanned: 2 > groups_considered: 2 > extents_scanned: 2 > goal_hits: 1 > 2^n_hits: 2 > breaks: 0 > lost: 0 > useless_c0_loops: 0 > useless_c1_loops: 0 > useless_c2_loops: 0 > useless_c3_loops: 0 > buddies_generated: 60/969 > buddies_time_used: 2870959 > preallocated: 5626 > discarded: 0 > [root@CO82 ~]# > > Second looks more rational. > > Best regards, > Artem Blagodarenko. > > > On 9 Feb 2021, at 23:28, Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx> wrote: > > > > 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 > > > > Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx> > > --- > > fs/ext4/ext4.h | 4 ++++ > > fs/ext4/mballoc.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++- > > fs/ext4/mballoc.h | 1 + > > fs/ext4/sysfs.c | 2 ++ > > 4 files changed, 57 insertions(+), 1 deletion(-) > > > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > > index 6dd127942208..317b43420ecf 100644 > > --- a/fs/ext4/ext4.h > > +++ b/fs/ext4/ext4.h > > @@ -1549,6 +1549,8 @@ 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_considered; /* number of groups considered */ > > + 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 */ > > @@ -1558,6 +1560,7 @@ struct ext4_sb_info { > > atomic_t s_mb_preallocated; > > atomic_t s_mb_discarded; > > atomic_t s_lock_busy; > > + atomic64_t s_bal_cX_failed[4]; /* cX loop didn't find blocks */ > > > > /* locality groups */ > > struct ext4_locality_group __percpu *s_locality_groups; > > @@ -2808,6 +2811,7 @@ 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 07b78a3cc421..fffd0770e930 100644 > > --- a/fs/ext4/mballoc.c > > +++ b/fs/ext4/mballoc.c > > @@ -2083,6 +2083,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac, > > > > BUG_ON(cr < 0 || cr >= 4); > > > > + ac->ac_groups_considered++; > > if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp))) > > return false; > > > > @@ -2420,6 +2421,9 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) > > 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 && > > @@ -2548,6 +2552,48 @@ 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_printf(seq, "\tgroups_considered: %u\n", atomic_read(&sbi->s_bal_groups_considered)); > > + 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, "\tuseless_c0_loops: %llu\n", > > + (unsigned long long)atomic64_read(&sbi->s_bal_cX_failed[0])); > > + seq_printf(seq, "\tuseless_c1_loops: %llu\n", > > + (unsigned long long)atomic64_read(&sbi->s_bal_cX_failed[1])); > > + seq_printf(seq, "\tuseless_c2_loops: %llu\n", > > + (unsigned long long)atomic64_read(&sbi->s_bal_cX_failed[2])); > > + seq_printf(seq, "\tuseless_c3_loops: %llu\n", > > + (unsigned long long)atomic64_read(&sbi->s_bal_cX_failed[3])); > > + 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; > > @@ -2968,9 +3014,10 @@ 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), > > @@ -3579,6 +3626,8 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac) > > 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); > > + atomic_add(ac->ac_groups_considered, &sbi->s_bal_groups_considered); > > 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/mballoc.h b/fs/ext4/mballoc.h > > index e75b4749aa1c..7597330dbdf8 100644 > > --- a/fs/ext4/mballoc.h > > +++ b/fs/ext4/mballoc.h > > @@ -161,6 +161,7 @@ struct ext4_allocation_context { > > /* copy of the best found extent taken before preallocation efforts */ > > struct ext4_free_extent ac_f_ex; > > > > + __u32 ac_groups_considered; > > __u16 ac_groups_scanned; > > __u16 ac_found; > > __u16 ac_tail; > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > > index 4e27fe6ed3ae..752d1c261e2a 100644 > > --- a/fs/ext4/sysfs.c > > +++ b/fs/ext4/sysfs.c > > @@ -527,6 +527,8 @@ 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; > > } > > -- > > 2.30.0.478.g8a0d178c01-goog > > >