Re: [PATCH v2 2/3] ext4: limit the length of per-inode prealloc list

From: brookxu
Date: Wed Aug 05 2020 - 05:18:47 EST

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Add more... , As we expected, the running time of the test process is
reduced significantly.

Running time on unrepaired kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m2.051s
user    0m0.008s
sys    0m2.026s

Running time on repaired kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m0.471s
user    0m0.004s
sys        0m0.395s

Thanks.

Andreas Dilger wrote on 2020/8/5 12:53:
> On Aug 4, 2020, at 7:02 PM, brookxu <brookxu.cn@xxxxxxxxx> wrote:
>> In the scenario of writing sparse files, the Per-inode prealloc list may
>> be very long, resulting in high overhead for ext4_mb_use_preallocated().
>> To circumvent this problem, we limit the maximum length of per-inode
>> prealloc list to 512 and allow users to modify it.
>>
>> Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
> Do you have any kind of measurements that show the benefit of this patch?
> For example performance improvement, memory or CPU usage before and after?
> How long is "very long"?
>
> Cheers, Andreas
>
>> ---
>> fs/ext4/ext4.h | 3 ++-
>> fs/ext4/extents.c | 10 ++++-----
>> fs/ext4/file.c | 2 +-
>> fs/ext4/indirect.c | 2 +-
>> fs/ext4/inode.c | 6 +++---
>> fs/ext4/ioctl.c | 2 +-
>> fs/ext4/mballoc.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++----
>> fs/ext4/mballoc.h | 4 ++++
>> fs/ext4/move_extent.c | 4 ++--
>> fs/ext4/super.c | 2 +-
>> fs/ext4/sysfs.c | 2 ++
>> 11 files changed, 75 insertions(+), 19 deletions(-)
>>
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index 42f5060..68e0ebe 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -1501,6 +1501,7 @@ struct ext4_sb_info {
>> unsigned int s_mb_stats;
>> unsigned int s_mb_order2_reqs;
>> unsigned int s_mb_group_prealloc;
>> + unsigned int s_mb_max_inode_prealloc;
>> unsigned int s_max_dir_size_kb;
>> /* where last allocation was done - for stream allocation */
>> unsigned long s_mb_last_group;
>> @@ -2651,7 +2652,7 @@ extern int ext4_init_inode_table(struct super_block *sb,
>> extern ext4_fsblk_t ext4_mb_new_blocks(handle_t *,
>> struct ext4_allocation_request *, int *);
>> extern int ext4_mb_reserve_blocks(struct super_block *, int);
>> -extern void ext4_discard_preallocations(struct inode *);
>> +extern void ext4_discard_preallocations(struct inode *, unsigned int);
>> extern int __init ext4_init_mballoc(void);
>> extern void ext4_exit_mballoc(void);
>> extern void ext4_free_blocks(handle_t *handle, struct inode *inode,
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 221f240..a40f928 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -100,7 +100,7 @@ static int ext4_ext_trunc_restart_fn(struct inode *inode, int *dropped)
>> * i_mutex. So we can safely drop the i_data_sem here.
>> */
>> BUG_ON(EXT4_JOURNAL(inode) == NULL);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> up_write(&EXT4_I(inode)->i_data_sem);
>> *dropped = 1;
>> return 0;
>> @@ -4272,7 +4272,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>> * not a good idea to call discard here directly,
>> * but otherwise we'd need to call it every free().
>> */
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
>> fb_flags = EXT4_FREE_BLOCKS_NO_QUOT_UPDATE;
>> ext4_free_blocks(handle, inode, NULL, newblock,
>> @@ -5299,7 +5299,7 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
>> }
>>
>> down_write(&EXT4_I(inode)->i_data_sem);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> ret = ext4_es_remove_extent(inode, punch_start,
>> EXT_MAX_BLOCKS - punch_start);
>> @@ -5313,7 +5313,7 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
>> up_write(&EXT4_I(inode)->i_data_sem);
>> goto out_stop;
>> }
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> ret = ext4_ext_shift_extents(inode, handle, punch_stop,
>> punch_stop - punch_start, SHIFT_LEFT);
>> @@ -5445,7 +5445,7 @@ static int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
>> goto out_stop;
>>
>> down_write(&EXT4_I(inode)->i_data_sem);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> path = ext4_find_extent(inode, offset_lblk, NULL, 0);
>> if (IS_ERR(path)) {
>> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
>> index 2a01e31..e3ab8ea 100644
>> --- a/fs/ext4/file.c
>> +++ b/fs/ext4/file.c
>> @@ -148,7 +148,7 @@ static int ext4_release_file(struct inode *inode, struct file *filp)
>> !EXT4_I(inode)->i_reserved_data_blocks)
>> {
>> down_write(&EXT4_I(inode)->i_data_sem);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> up_write(&EXT4_I(inode)->i_data_sem);
>> }
>> if (is_dx(inode) && filp->private_data)
>> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
>> index be2b66e..ec6b930 100644
>> --- a/fs/ext4/indirect.c
>> +++ b/fs/ext4/indirect.c
>> @@ -696,7 +696,7 @@ static int ext4_ind_trunc_restart_fn(handle_t *handle, struct inode *inode,
>> * i_mutex. So we can safely drop the i_data_sem here.
>> */
>> BUG_ON(EXT4_JOURNAL(inode) == NULL);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> up_write(&EXT4_I(inode)->i_data_sem);
>> *dropped = 1;
>> return 0;
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index 10dd470..bb9e1cd 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -383,7 +383,7 @@ void ext4_da_update_reserve_space(struct inode *inode,
>> */
>> if ((ei->i_reserved_data_blocks == 0) &&
>> !inode_is_open_for_write(inode))
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> }
>>
>> static int __check_block_validity(struct inode *inode, const char *func,
>> @@ -4056,7 +4056,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
>> if (stop_block > first_block) {
>>
>> down_write(&EXT4_I(inode)->i_data_sem);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> ret = ext4_es_remove_extent(inode, first_block,
>> stop_block - first_block);
>> @@ -4211,7 +4211,7 @@ int ext4_truncate(struct inode *inode)
>>
>> down_write(&EXT4_I(inode)->i_data_sem);
>>
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
>> err = ext4_ext_truncate(handle, inode);
>> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
>> index 999cf6a..a5fcc23 100644
>> --- a/fs/ext4/ioctl.c
>> +++ b/fs/ext4/ioctl.c
>> @@ -202,7 +202,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
>> reset_inode_seed(inode);
>> reset_inode_seed(inode_bl);
>>
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>>
>> err = ext4_mark_inode_dirty(handle, inode);
>> if (err < 0) {
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index 4f21f34..28a139f 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -2736,6 +2736,7 @@ int ext4_mb_init(struct super_block *sb)
>> sbi->s_mb_stats = MB_DEFAULT_STATS;
>> sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
>> sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;
>> + sbi->s_mb_max_inode_prealloc = MB_DEFAULT_MAX_INODE_PREALLOC;
>> /*
>> * The default group preallocation is 512, which for 4k block
>> * sizes translates to 2 megabytes. However for bigalloc file
>> @@ -4103,7 +4104,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>> *
>> * FIXME!! Make sure it is valid at all the call sites
>> */
>> -void ext4_discard_preallocations(struct inode *inode)
>> +void ext4_discard_preallocations(struct inode *inode, unsigned int needed)
>> {
>> struct ext4_inode_info *ei = EXT4_I(inode);
>> struct super_block *sb = inode->i_sb;
>> @@ -4121,15 +4122,18 @@ void ext4_discard_preallocations(struct inode *inode)
>>
>> mb_debug(sb, "discard preallocation for inode %lu\n",
>> inode->i_ino);
>> - trace_ext4_discard_preallocations(inode);
>> + trace_ext4_discard_preallocations(inode, needed);
>>
>> INIT_LIST_HEAD(&list);
>>
>> + if (needed == 0)
>> + needed = UINT_MAX;
>> +
>> repeat:
>> /* first, collect all pa's in the inode */
>> spin_lock(&ei->i_prealloc_lock);
>> - while (!list_empty(&ei->i_prealloc_list)) {
>> - pa = list_entry(ei->i_prealloc_list.next,
>> + while (!list_empty(&ei->i_prealloc_list) && needed) {
>> + pa = list_entry(ei->i_prealloc_list.prev,
>> struct ext4_prealloc_space, pa_inode_list);
>> BUG_ON(pa->pa_obj_lock != &ei->i_prealloc_lock);
>> spin_lock(&pa->pa_lock);
>> @@ -4150,6 +4154,7 @@ void ext4_discard_preallocations(struct inode *inode)
>> spin_unlock(&pa->pa_lock);
>> list_del_rcu(&pa->pa_inode_list);
>> list_add(&pa->u.pa_tmp_list, &list);
>> + needed--;
>> continue;
>> }
>>
>> @@ -4549,10 +4554,42 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
>> }
>>
>> /*
>> + * if per-inode prealloc list is too long, trim some PA
>> + */
>> +static void
>> +ext4_mb_trim_inode_pa(struct inode *inode)
>> +{
>> + struct ext4_inode_info *ei = EXT4_I(inode);
>> + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
>> + struct ext4_prealloc_space *pa;
>> + int count = 0, delta;
>> +
>> + rcu_read_lock();
>> + list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
>> + spin_lock(&pa->pa_lock);
>> + if (pa->pa_deleted) {
>> + spin_unlock(&pa->pa_lock);
>> + continue;
>> + }
>> + count++;
>> + spin_unlock(&pa->pa_lock);
>> + }
>> + rcu_read_unlock();
>> +
>> + delta = (sbi->s_mb_max_inode_prealloc >> 2) + 1;
>> + if (count > sbi->s_mb_max_inode_prealloc + delta) {
>> + count -= sbi->s_mb_max_inode_prealloc;
>> + ext4_discard_preallocations(inode, count);
>> + }
>> +}
>> +
>> +/*
>> * release all resource we used in allocation
>> */
>> static int ext4_mb_release_context(struct ext4_allocation_context *ac)
>> {
>> + struct inode *inode = ac->ac_inode;
>> + struct ext4_inode_info *ei = EXT4_I(inode);
>> struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
>> struct ext4_prealloc_space *pa = ac->ac_pa;
>> if (pa) {
>> @@ -4578,6 +4615,17 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
>> ext4_mb_add_n_trim(ac);
>> }
>> }
>> +
>> + if (pa->pa_type == MB_INODE_PA) {
>> + /*
>> + * treat per-inode prealloc list as a lru list, then try
>> + * to trim the least recently used PA.
>> + */
>> + spin_lock(pa->pa_obj_lock);
>> + list_move(&ei->i_prealloc_list, &pa->pa_inode_list);
>> + spin_unlock(pa->pa_obj_lock);
>> + }
>> +
>> ext4_mb_put_pa(ac, ac->ac_sb, pa);
>> }
>> if (ac->ac_bitmap_page)
>> @@ -4587,6 +4635,7 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
>> if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
>> mutex_unlock(&ac->ac_lg->lg_mutex);
>> ext4_mb_collect_stats(ac);
>> + ext4_mb_trim_inode_pa(inode);
>> return 0;
>> }
>>
>> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
>> index 6b4d17c..e75b474 100644
>> --- a/fs/ext4/mballoc.h
>> +++ b/fs/ext4/mballoc.h
>> @@ -73,6 +73,10 @@
>> */
>> #define MB_DEFAULT_GROUP_PREALLOC 512
>>
>> +/*
>> + * maximum length of inode prealloc list
>> + */
>> +#define MB_DEFAULT_MAX_INODE_PREALLOC 512
>>
>> struct ext4_free_data {
>> /* this links the free block information from sb_info */
>> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
>> index 1ed86fb..0d601b8 100644
>> --- a/fs/ext4/move_extent.c
>> +++ b/fs/ext4/move_extent.c
>> @@ -686,8 +686,8 @@
>>
>> out:
>> if (*moved_len) {
>> - ext4_discard_preallocations(orig_inode);
>> - ext4_discard_preallocations(donor_inode);
>> + ext4_discard_preallocations(orig_inode, 0);
>> + ext4_discard_preallocations(donor_inode, 0);
>> }
>>
>> ext4_ext_drop_refs(path);
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index 330957e..8ce61f3 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -1216,7 +1216,7 @@ void ext4_clear_inode(struct inode *inode)
>> {
>> invalidate_inode_buffers(inode);
>> clear_inode(inode);
>> - ext4_discard_preallocations(inode);
>> + ext4_discard_preallocations(inode, 0);
>> ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);
>> dquot_drop(inode);
>> if (EXT4_I(inode)->jinode) {
>> diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
>> index 6c9fc9e..92f04e9 100644
>> --- a/fs/ext4/sysfs.c
>> +++ b/fs/ext4/sysfs.c
>> @@ -215,6 +215,7 @@ static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf)
>> EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
>> EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
>> EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);
>> +EXT4_RW_ATTR_SBI_UI(mb_max_inode_prealloc, s_mb_max_inode_prealloc);
>> EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb);
>> EXT4_ATTR(trigger_fs_error, 0200, trigger_test_error);
>> EXT4_RW_ATTR_SBI_UI(err_ratelimit_interval_ms, s_err_ratelimit_state.interval);
>> @@ -257,6 +258,7 @@ static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf)
>> ATTR_LIST(mb_order2_req),
>> ATTR_LIST(mb_stream_req),
>> ATTR_LIST(mb_group_prealloc),
>> + ATTR_LIST(mb_max_inode_prealloc),
>> ATTR_LIST(max_writeback_mb_bump),
>> ATTR_LIST(extent_max_zeroout_kb),
>> ATTR_LIST(trigger_fs_error),
>>
>> --
>> 1.8.3.1
>>
>
> Cheers, Andreas
>
>
>
>
>

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