hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/ICAH6I -------------------------------- When ext4 allocates blocks, we used to just go through the block groups one by one to find a good one. But when there are tons of block groups (like hundreds of thousands or even millions) and not many have free space (meaning they're mostly full), it takes a really long time to check them all, and performance gets bad. So, we added the "mb_optimize_scan" mount option (which is on by default now). It keeps track of some group lists, so when we need a free block, we can just grab a likely group from the right list. This saves time and makes block allocation much faster. But when multiple processes or containers are doing similar things, like constantly allocating 8k blocks, they all try to use the same block group in the same list. Even just two processes doing this can cut the IOPS in half. For example, one container might do 300,000 IOPS, but if you run two at the same time, the total is only 150,000. Since we can already look at block groups in a non-linear way, the first and last groups in the same list are basically the same for finding a block right now. Therefore, add an ext4_try_lock_group() helper function to skip the current group when it is locked by another process, thereby avoiding contention with other processes. This helps ext4 make better use of having multiple block groups. Also, to make sure we don't skip all the groups that have free space when allocating blocks, we won't try to skip busy groups anymore when ac_criteria is CR_ANY_FREE. Performance test data follows: CPU: HUAWEI Kunpeng 920 Memory: 480GB Disk: 480GB SSD SATA 3.2 Test: Running will-it-scale/fallocate2 on 64 CPU-bound containers. Observation: Average fallocate operations per container per second. base patched mb_optimize_scan=0 3588 6755 (+88.2%) mb_optimize_scan=1 3588 4302 (+19.8%) Signed-off-by: Baokun Li <libaokun1@huawei.com> --- fs/ext4/ext4.h | 23 ++++++++++++++--------- fs/ext4/mballoc.c | 14 +++++++++++--- 2 files changed, 25 insertions(+), 12 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 6fcbb2184d1b..885fe1d9a8e9 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3487,23 +3487,28 @@ static inline int ext4_fs_is_busy(struct ext4_sb_info *sbi) return (atomic_read(&sbi->s_lock_busy) > EXT4_CONTENTION_THRESHOLD); } +static inline bool ext4_try_lock_group(struct super_block *sb, ext4_group_t group) +{ + if (!spin_trylock(ext4_group_lock_ptr(sb, group))) + return false; + /* + * We're able to grab the lock right away, so drop the lock + * contention counter. + */ + atomic_add_unless(&EXT4_SB(sb)->s_lock_busy, -1, 0); + return true; +} + static inline void ext4_lock_group(struct super_block *sb, ext4_group_t group) { - spinlock_t *lock = ext4_group_lock_ptr(sb, group); - if (spin_trylock(lock)) - /* - * We're able to grab the lock right away, so drop the - * lock contention counter. - */ - atomic_add_unless(&EXT4_SB(sb)->s_lock_busy, -1, 0); - else { + if (!ext4_try_lock_group(sb, group)) { /* * The lock is busy, so bump the contention counter, * and then wait on the spin lock. */ atomic_add_unless(&EXT4_SB(sb)->s_lock_busy, 1, EXT4_MAX_CONTENTION); - spin_lock(lock); + spin_lock(ext4_group_lock_ptr(sb, group)); } } diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 7c8cb88b426e..7646ac5d3b6f 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -899,7 +899,8 @@ static void ext4_mb_choose_next_group_p2_aligned(struct ext4_allocation_context bb_largest_free_order_node) { if (sbi->s_mb_stats) atomic64_inc(&sbi->s_bal_cX_groups_considered[CR_POWER2_ALIGNED]); - if (likely(ext4_mb_good_group(ac, iter->bb_group, CR_POWER2_ALIGNED))) { + if (likely(ext4_mb_good_group(ac, iter->bb_group, CR_POWER2_ALIGNED)) && + !spin_is_locked(ext4_group_lock_ptr(ac->ac_sb, iter->bb_group))) { *group = iter->bb_group; ac->ac_flags |= EXT4_MB_CR_POWER2_ALIGNED_OPTIMIZED; read_unlock(&sbi->s_mb_largest_free_orders_locks[i]); @@ -935,7 +936,8 @@ ext4_mb_find_good_group_avg_frag_lists(struct ext4_allocation_context *ac, int o list_for_each_entry(iter, frag_list, bb_avg_fragment_size_node) { if (sbi->s_mb_stats) atomic64_inc(&sbi->s_bal_cX_groups_considered[cr]); - if (likely(ext4_mb_good_group(ac, iter->bb_group, cr))) { + if (likely(ext4_mb_good_group(ac, iter->bb_group, cr)) && + !spin_is_locked(ext4_group_lock_ptr(ac->ac_sb, iter->bb_group))) { grp = iter; break; } @@ -2911,7 +2913,13 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) if (err) goto out; - ext4_lock_group(sb, group); + /* skip busy group */ + if (cr >= CR_ANY_FREE) { + ext4_lock_group(sb, group); + } else if (!ext4_try_lock_group(sb, group)) { + ext4_mb_unload_buddy(&e4b); + continue; + } /* * We need to check again after locking the -- 2.46.1