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ext4: drop s_mb_bal_lock and convert protected fields to atomic

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s_mb_buddies_generated gets used later in this patch series to
determine if the cr 0 and cr 1 optimziations should be performed or
not. Currently, s_mb_buddies_generated is protected under a
spin_lock. In the allocation path, it is better if we don't depend on
the lock and instead read the value atomically. In order to do that,
we drop s_bal_lock altogether and we convert the only two protected
fields by it s_mb_buddies_generated and s_mb_generation_time to atomic
type.

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/20210401172129.189766-2-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Harshad Shirwadkar 2021-04-01 10:21:23 -07:00 committed by Theodore Ts'o
parent a149d2a5ca
commit 67d2518604
2 changed files with 7 additions and 11 deletions
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5
fs/ext4/ext4.h
View file

@ -1553,9 +1553,8 @@ struct ext4_sb_info {
atomic_t s_bal_goals; /* goal hits */
atomic_t s_bal_breaks; /* too long searches */
atomic_t s_bal_2orders; /* 2^order hits */
spinlock_t s_bal_lock;
unsigned long s_mb_buddies_generated;
unsigned long long s_mb_generation_time;
atomic_t s_mb_buddies_generated; /* number of buddies generated */
atomic64_t s_mb_generation_time;
atomic_t s_mb_lost_chunks;
atomic_t s_mb_preallocated;
atomic_t s_mb_discarded;

13
fs/ext4/mballoc.c
View file

@ -816,10 +816,8 @@ void ext4_mb_generate_buddy(struct super_block *sb,
clear_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
period = get_cycles() - period;
spin_lock(&sbi->s_bal_lock);
sbi->s_mb_buddies_generated++;
sbi->s_mb_generation_time += period;
spin_unlock(&sbi->s_bal_lock);
atomic_inc(&sbi->s_mb_buddies_generated);
atomic64_add(period, &sbi->s_mb_generation_time);
}
/* The buddy information is attached the buddy cache inode
@ -2850,7 +2848,6 @@ int ext4_mb_init(struct super_block *sb)
} while (i <= sb->s_blocksize_bits + 1);
spin_lock_init(&sbi->s_md_lock);
spin_lock_init(&sbi->s_bal_lock);
sbi->s_mb_free_pending = 0;
INIT_LIST_HEAD(&sbi->s_freed_data_list);
@ -2986,9 +2983,9 @@ int ext4_mb_release(struct super_block *sb)
atomic_read(&sbi->s_bal_breaks),
atomic_read(&sbi->s_mb_lost_chunks));
ext4_msg(sb, KERN_INFO,
"mballoc: %lu generated and it took %Lu",
sbi->s_mb_buddies_generated,
sbi->s_mb_generation_time);
"mballoc: %u generated and it took %llu",
atomic_read(&sbi->s_mb_buddies_generated),
atomic64_read(&sbi->s_mb_generation_time));
ext4_msg(sb, KERN_INFO,
"mballoc: %u preallocated, %u discarded",
atomic_read(&sbi->s_mb_preallocated),