Re: [PATCH 2/4] ext4: drop s_mb_bal_lock and convert protected fields to atomic
From: Andreas Dilger <hidden>
Date: 2021-01-30 09:24:10
On Jan 29, 2021, at 3:29 PM, Harshad Shirwadkar [off-list ref] wrote:
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 <redacted>
Reviewed-by: Andreas Dilger <redacted>
quoted hunk ↗ jump to hunk
--- fs/ext4/ext4.h | 5 ++--- fs/ext4/mballoc.c | 13 +++++-------- 2 files changed, 7 insertions(+), 11 deletions(-)diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 64f25ea2fa7a..6dd127942208 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h@@ -1552,9 +1552,8 @@ 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;diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 625242e5c683..11c56b0e6f35 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c@@ -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@@ -2844,7 +2842,6 @@ int ext4_mb_init(struct super_block *sb)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);@@ -2980,9 +2977,9 @@ 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), -- 2.30.0.365.g02bc693789-goog
Cheers, Andreas
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