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Message-Id: <A86257DC-98BF-482B-ADBE-65B220E133E6@gmail.com>
Date: Fri, 12 Feb 2021 19:52:00 +0300
From: Благодаренко Артём
<artem.blagodarenko@...il.com>
To: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: linux-ext4@...r.kernel.org, "Theodore Y. Ts'o" <tytso@....edu>,
bzzz@...mcloud.com, sihara@....com,
Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH v2 2/5] ext4: add mballoc stats proc file
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@...2 ~]# 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@...2 ~]# 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@...2 ~]#
And location that suggested
[root@...2 ~]# 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@...2 ~]# 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@...2 ~]#
Second looks more rational.
Best regards,
Artem Blagodarenko.
> On 9 Feb 2021, at 23:28, Harshad Shirwadkar <harshadshirwadkar@...il.com> 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@...il.com>
> ---
> 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
>
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