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Message-ID: <685bee8d-2909-a332-8362-2e0e073fb8e3@huawei.com>
Date: Tue, 21 Aug 2018 11:26:18 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-kernel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v4] f2fs: fix performance issue observed with
multi-thread sequential read
On 2018/8/21 10:28, Jaegeuk Kim wrote:
> On 08/20, Chao Yu wrote:
>> On 2018/8/18 2:29, Jaegeuk Kim wrote:
>>> This reverts the commit - "b93f771 - f2fs: remove writepages lock"
>>> to fix the drop in sequential read throughput.
>>>
>>> Test: ./tiotest -t 32 -d /data/tio_tmp -f 32 -b 524288 -k 1 -k 3 -L
>>> device: UFS
>>>
>>> Before -
>>> read throughput: 185 MB/s
>>> total read requests: 85177 (of these ~80000 are 4KB size requests).
>>> total write requests: 2546 (of these ~2208 requests are written in 512KB).
>>>
>>> After -
>>> read throughput: 758 MB/s
>>> total read requests: 2417 (of these ~2042 are 512KB reads).
>>> total write requests: 2701 (of these ~2034 requests are written in 512KB).
>>>
>>> Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>> ---
>>>
>>> Change log from v3:
>>> - add more conditions to serialize the allocation
>>>
>>> Documentation/ABI/testing/sysfs-fs-f2fs | 8 ++++++++
>>> fs/f2fs/data.c | 10 ++++++++++
>>> fs/f2fs/f2fs.h | 2 ++
>>> fs/f2fs/segment.c | 1 +
>>> fs/f2fs/super.c | 1 +
>>> fs/f2fs/sysfs.c | 2 ++
>>> 6 files changed, 24 insertions(+)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>> index 9b0123388f18..94a24aedcdb2 100644
>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>> @@ -51,6 +51,14 @@ Description:
>>> Controls the dirty page count condition for the in-place-update
>>> policies.
>>>
>>> +What: /sys/fs/f2fs/<disk>/min_seq_blocks
>>> +Date: August 2018
>>> +Contact: "Jaegeuk Kim" <jaegeuk@...nel.org>
>>> +Description:
>>> + Controls the dirty page count condition for batched sequential
>>> + writes in ->writepages.
>>> +
>>> +
>>> What: /sys/fs/f2fs/<disk>/min_hot_blocks
>>> Date: March 2017
>>> Contact: "Jaegeuk Kim" <jaegeuk@...nel.org>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 43d3723dc886..fb63425ea242 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2130,6 +2130,7 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
>>> struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>> struct blk_plug plug;
>>> int ret;
>>> + bool locked = false;
>>>
>>> /* deal with chardevs and other special file */
>>> if (!mapping->a_ops->writepage)
>>> @@ -2160,10 +2161,19 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
>>> else if (atomic_read(&sbi->wb_sync_req[DATA]))
>>> goto skip_write;
>>>
>>> + if (!S_ISDIR(inode->i_mode) && (wbc->sync_mode != WB_SYNC_ALL ||
>>> + get_dirty_pages(inode) <= SM_I(sbi)->min_seq_blocks)) {
>>
>> get_dirty_pages(inode) >= SM_I(sbi)->min_seq_blocks
>
> Oops. :P
>
>>
>>> + mutex_lock(&sbi->writepages);
>>
>> Still didn't see atomic write being covered by this lock.
>
> Taking a look at this again, I'm in doubt to cover this, since 1) normal usecase
> of atomic writes is to set page dirty and write it right away during commit, 2)
> there'd be no large number of dirty pages even when we consider race condition
> between writepages and atomic_commit. Am I missing another case?
Yup, reasonable, hot type data is not fit for this optimization, due to easily
defragmenting, and small size. :)
Thanks,
>
>>
>> How about introducing a macro like __should_serialize_io() for indicating the
>> condition in where we should serialize IOs.
>
> Done.
>
> Thank you for ths suggestion.
>
>>
>> Thanks,
>>
>>> + locked = true;
>>> + }
>>> +
>>> blk_start_plug(&plug);
>>> ret = f2fs_write_cache_pages(mapping, wbc, io_type);
>>> blk_finish_plug(&plug);
>>>
>>> + if (locked)
>>> + mutex_unlock(&sbi->writepages);
>>> +
>>> if (wbc->sync_mode == WB_SYNC_ALL)
>>> atomic_dec(&sbi->wb_sync_req[DATA]);
>>> /*
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 9a6ba4a8d338..170573f8a04a 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -913,6 +913,7 @@ struct f2fs_sm_info {
>>> unsigned int ipu_policy; /* in-place-update policy */
>>> unsigned int min_ipu_util; /* in-place-update threshold */
>>> unsigned int min_fsync_blocks; /* threshold for fsync */
>>> + unsigned int min_seq_blocks; /* threshold for sequential blocks */
>>> unsigned int min_hot_blocks; /* threshold for hot block allocation */
>>> unsigned int min_ssr_sections; /* threshold to trigger SSR allocation */
>>>
>>> @@ -1133,6 +1134,7 @@ struct f2fs_sb_info {
>>> struct rw_semaphore sb_lock; /* lock for raw super block */
>>> int valid_super_block; /* valid super block no */
>>> unsigned long s_flag; /* flags for sbi */
>>> + struct mutex writepages; /* mutex for writepages() */
>>>
>>> #ifdef CONFIG_BLK_DEV_ZONED
>>> unsigned int blocks_per_blkz; /* F2FS blocks per zone */
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index b136e39e1e9e..20650e25117b 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -4127,6 +4127,7 @@ int f2fs_build_segment_manager(struct f2fs_sb_info *sbi)
>>> sm_info->ipu_policy = 1 << F2FS_IPU_FSYNC;
>>> sm_info->min_ipu_util = DEF_MIN_IPU_UTIL;
>>> sm_info->min_fsync_blocks = DEF_MIN_FSYNC_BLOCKS;
>>> + sm_info->min_seq_blocks = sbi->blocks_per_seg * sbi->segs_per_sec;
>>> sm_info->min_hot_blocks = DEF_MIN_HOT_BLOCKS;
>>> sm_info->min_ssr_sections = reserved_sections(sbi);
>>>
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index c6e4750a9187..6b6cb4eb8439 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -2864,6 +2864,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>> /* init f2fs-specific super block info */
>>> sbi->valid_super_block = valid_super_block;
>>> mutex_init(&sbi->gc_mutex);
>>> + mutex_init(&sbi->writepages);
>>> mutex_init(&sbi->cp_mutex);
>>> init_rwsem(&sbi->node_write);
>>> init_rwsem(&sbi->node_change);
>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>> index cd2e030e47b8..81c0e5337443 100644
>>> --- a/fs/f2fs/sysfs.c
>>> +++ b/fs/f2fs/sysfs.c
>>> @@ -397,6 +397,7 @@ F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
>>> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
>>> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
>>> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_fsync_blocks, min_fsync_blocks);
>>> +F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_seq_blocks, min_seq_blocks);
>>> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_hot_blocks, min_hot_blocks);
>>> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ssr_sections, min_ssr_sections);
>>> F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ram_thresh, ram_thresh);
>>> @@ -449,6 +450,7 @@ static struct attribute *f2fs_attrs[] = {
>>> ATTR_LIST(ipu_policy),
>>> ATTR_LIST(min_ipu_util),
>>> ATTR_LIST(min_fsync_blocks),
>>> + ATTR_LIST(min_seq_blocks),
>>> ATTR_LIST(min_hot_blocks),
>>> ATTR_LIST(min_ssr_sections),
>>> ATTR_LIST(max_victim_search),
>>>
>
> .
>
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