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Message-ID: <7194f3d2-b875-376a-4c46-37c598bf3e8e@huawei.com>
Date: Tue, 14 Aug 2018 14:18:09 +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 v3] f2fs: fix performance issue observed with
multi-thread sequential read
On 2018/8/14 12:04, Jaegeuk Kim wrote:
> On 08/14, Chao Yu wrote:
>> On 2018/8/14 4:11, Jaegeuk Kim wrote:
>>> On 08/13, Chao Yu wrote:
>>>> Hi Jaegeuk,
>>>>
>>>> On 2018/8/11 2:56, 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).
>>>>
>>>> IMO, it only impact sequential read performance in a large file which may be
>>>> fragmented during multi-thread writing.
>>>>
>>>> In android environment, mostly, the large file should be cold type, such as apk,
>>>> mp3, rmvb, jpeg..., so I think we only need to serialize writepages() for cold
>>>> data area writer.
>>>>
>>>> So how about adding a mount option to serialize writepage() for different type
>>>> of log, e.g. in android, using serialize=4; by default, using serialize=7
>>>> HOT_DATA 1
>>>> WARM_DATA 2
>>>> COLD_DATA 4
>>>
>>> Well, I don't think we need to give too many mount options for this fragmented
>>> case. How about doing this for the large files only like this?
>>
>> Thread A write 512 pages Thread B write 8 pages
>>
>> - writepages()
>> - mutex_lock(&sbi->writepages);
>> - writepage();
>> ...
>> - writepages()
>> - writepage()
>> ....
>> - writepage();
>> ...
>> - mutex_unlock(&sbi->writepages);
>>
>> Above case will also cause fragmentation since we didn't serialize all
>> concurrent IO with the lock.
>>
>> Do we need to consider such case?
>
> We can simply allow 512 and 8 in the same segment, which would not a big deal,
> when considering starvation of Thread B.
Yeah, but in reality, there would be more threads competing in same log header,
so I worry that the effect of defragmenting will not so good as we expect,
anyway, for benchmark, it's enough.
Thanks,
>
>>
>> Thanks,
>>
>>>
>>> >From 4fea0b6e4da8512a72dd52afc7a51beb35966ad9 Mon Sep 17 00:00:00 2001
>>> From: Jaegeuk Kim <jaegeuk@...nel.org>
>>> Date: Thu, 9 Aug 2018 17:53:34 -0700
>>> Subject: [PATCH] f2fs: fix performance issue observed with multi-thread
>>> sequential read
>>>
>>> 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>
>>> ---
>>> 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 45f043ee48bd..f09231b1cc74 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2132,6 +2132,7 @@ 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)
>>> @@ -2162,10 +2163,19 @@ 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) &&
>>> + get_dirty_pages(inode) <= SM_I(sbi)->min_seq_blocks) {
>>> + mutex_lock(&sbi->writepages);
>>> + 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 375aa9f30cfa..098bdedc28bf 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 63fc647f9ac2..ffea2d1303bd 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -4131,6 +4131,7 @@ 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 be41dbd7b261..53d70b64fea1 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -2842,6 +2842,7 @@ 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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