Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 2/2] f2fs: tune discard speed with storage usage rate
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20180810100806.9298-1-yuchao0@huawei.com>
 <20180810100806.9298-2-yuchao0@huawei.com>
 <20180814041906.GC52730@jaegeuk-macbookpro.roam.corp.google.com>
 <57d9b6ea-68a5-4736-0b34-74db539d8959@huawei.com>
 <20180814172313.GC56510@jaegeuk-macbookpro.roam.corp.google.com>
 <cf3e27a2-de20-13e7-eb5e-f0ad2781cf0f@huawei.com>
 <20180815023326.GB84720@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <17aa1e09-6bfd-eb67-0f28-e13d8bbb17ff@huawei.com>
Date:   Wed, 15 Aug 2018 10:51:17 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <20180815023326.GB84720@jaegeuk-macbookpro.roam.corp.google.com>
Content-Type: text/plain; charset="windows-1252"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2018/8/15 10:33, Jaegeuk Kim wrote:
> On 08/15, Chao Yu wrote:
>> On 2018/8/15 1:23, Jaegeuk Kim wrote:
>>> On 08/14, Chao Yu wrote:
>>>> On 2018/8/14 12:19, Jaegeuk Kim wrote:
>>>>> On 08/10, Chao Yu wrote:
>>>>>> Previously, discard speed was fixed mostly, and in high usage rate
>>>>>> device, we will speed up issuing discard, but it doesn't make sense
>>>>>> that in a non-full filesystem, we still issue discard with slow speed.
>>>>>
>>>>> Could you please elaborate the problem in more detail? The speed depends
>>>>> on how many candidates?
>>>>
>>>> undiscard blocks are all 4k granularity.
>>>> a) utility: filesystem: 20% + undiscard blocks: 20% = flash storage: 40%
>>>> b) utility: filesystem: 40% + undiscard blocks: 25% = flash storage: 65%
>>>> c) utility: filesystem: 60% + undiscard blocks: 30% = flash storage: 100%
>>>>
>>>>
>>>> 1. for case c), we need to speed up issuing discard based on utilization of
>>>> "filesystem + undiscard" instead of just utilization of filesystem.
>>>>
>>>> -		if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
>>>> -			dpolicy->granularity = 1;
>>>> -			dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME;
>>>> -		}
>>>>
>>>> 2. If free space in storage touches therein threshold, performance will be very
>>>> sensitive. In low-end storage, with high usage in space, even free space is
>>>> reduced by 1%, performance will decrease a lot.
>>>
>>> So, we may need to distinguish low-end vs. high-end storage. In high-end case,
>>> it'd be better to avoid IO contention, while low-end device wants to get more
>>> discard commands as much as possible. So, how about adding an option for this
>>> as a tunable point?
>>
>> Agreed, how about adding a sysfs entry discard_tunning:
>> 1: enabled, use 4k granularity, self-adapted speed based on real device free space.
>> 0: disabled, use dcc->discard_granularity, fixed speed.
>>
>> By default: enabled
>>
>> How do you think?
> 
> I don't think this is proper with a sysfs entry, since we already know the

You mean by storage capacity? <= 32GB means low-end?

Thanks,

> device type when mounting the partition. We won't require to change the policy
> on the fly. And, I still don't get to change the default.
> 
>>
>> Thanks,
>>
>>>
>>>>
>>>> IMO, in above cases, we'd better to issue discard with high speed for c), middle
>>>> speed for b), and low speed for a).
>>>>
>>>> How do you think?
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>> Anyway, it comes out undiscarded block makes FTL GC be lower efficient
>>>>>> and causing high lifetime overhead.
>>>>>>
>>>>>> Let's tune discard speed as below:
>>>>>>
>>>>>> a. adjust default issue interval:
>>>>>> 		original	after
>>>>>> min_interval:	50ms		100ms
>>>>>> mid_interval:	500ms		1000ms
>>>>>> max_interval:	60000ms		10000ms
>>>>>>
>>>>>> b. if last time we stop issuing discard due to IO interruption of user,
>>>>>> let's reset all {min,mid,max}_interval to default one.
>>>>>>
>>>>>> c. tune {min,mid,max}_interval with below calculation method:
>>>>>>
>>>>>> base_interval = default_interval / 10;
>>>>>> total_interval = default_interval - base_interval;
>>>>>> interval = base_interval + total_interval * (100 - dev_util) / 100;
>>>>>>
>>>>>> For example:
>>>>>> min_interval (:100ms)
>>>>>> dev_util (%)	interval (ms)
>>>>>> 0		100
>>>>>> 10		91
>>>>>> 20		82
>>>>>> 30		73
>>>>>> ...
>>>>>> 80		28
>>>>>> 90		19
>>>>>> 100		10
>>>>>>
>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>>> ---
>>>>>>  fs/f2fs/f2fs.h    | 11 ++++----
>>>>>>  fs/f2fs/segment.c | 64 +++++++++++++++++++++++++++++++++++++----------
>>>>>>  fs/f2fs/segment.h |  9 +++++++
>>>>>>  fs/f2fs/super.c   |  2 +-
>>>>>>  4 files changed, 67 insertions(+), 19 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>> index 273ffdaf4891..a1dd2e1c3cb9 100644
>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>> @@ -185,10 +185,9 @@ enum {
>>>>>>  
>>>>>>  #define MAX_DISCARD_BLOCKS(sbi)		BLKS_PER_SEC(sbi)
>>>>>>  #define DEF_MAX_DISCARD_REQUEST		8	/* issue 8 discards per round */
>>>>>> -#define DEF_MIN_DISCARD_ISSUE_TIME	50	/* 50 ms, if exists */
>>>>>> -#define DEF_MID_DISCARD_ISSUE_TIME	500	/* 500 ms, if device busy */
>>>>>> -#define DEF_MAX_DISCARD_ISSUE_TIME	60000	/* 60 s, if no candidates */
>>>>>> -#define DEF_DISCARD_URGENT_UTIL		80	/* do more discard over 80% */
>>>>>> +#define DEF_MIN_DISCARD_ISSUE_TIME	100	/* 100 ms, if exists */
>>>>>> +#define DEF_MID_DISCARD_ISSUE_TIME	1000	/* 1000 ms, if device busy */
>>>>>> +#define DEF_MAX_DISCARD_ISSUE_TIME	10000	/* 10000 ms, if no candidates */
>>>>>>  #define DEF_CP_INTERVAL			60	/* 60 secs */
>>>>>>  #define DEF_IDLE_INTERVAL		5	/* 5 secs */
>>>>>>  
>>>>>> @@ -248,7 +247,8 @@ struct discard_entry {
>>>>>>  };
>>>>>>  
>>>>>>  /* default discard granularity of inner discard thread, unit: block count */
>>>>>> -#define DEFAULT_DISCARD_GRANULARITY		1
>>>>>> +#define MID_DISCARD_GRANULARITY			16
>>>>>> +#define MIN_DISCARD_GRANULARITY			1
>>>>>>  
>>>>>>  /* max discard pend list number */
>>>>>>  #define MAX_PLIST_NUM		512
>>>>>> @@ -330,6 +330,7 @@ struct discard_cmd_control {
>>>>>>  	atomic_t discard_cmd_cnt;		/* # of cached cmd count */
>>>>>>  	struct rb_root root;			/* root of discard rb-tree */
>>>>>>  	bool rbtree_check;			/* config for consistence check */
>>>>>> +	bool io_interrupted;			/* last state of io interrupted */
>>>>>>  };
>>>>>>  
>>>>>>  /* for the list of fsync inodes, used only during recovery */
>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>>> index 8b52e8dfb12f..9564aaf1f27b 100644
>>>>>> --- a/fs/f2fs/segment.c
>>>>>> +++ b/fs/f2fs/segment.c
>>>>>> @@ -968,6 +968,44 @@ static void __check_sit_bitmap(struct f2fs_sb_info *sbi,
>>>>>>  #endif
>>>>>>  }
>>>>>>  
>>>>>> +static void __adjust_discard_speed(unsigned int *interval,
>>>>>> +				unsigned int def_interval, int dev_util)
>>>>>> +{
>>>>>> +	unsigned int base_interval, total_interval;
>>>>>> +
>>>>>> +	base_interval = def_interval / 10;
>>>>>> +	total_interval = def_interval - base_interval;
>>>>>> +
>>>>>> +	/*
>>>>>> +	 * if def_interval = 100, adjusted interval should be in range of
>>>>>> +	 * [10, 100].
>>>>>> +	 */
>>>>>> +	*interval = base_interval + total_interval * (100 - dev_util) / 100;
>>>>>> +}
>>>>>> +
>>>>>> +static void __tune_discard_policy(struct f2fs_sb_info *sbi,
>>>>>> +					struct discard_policy *dpolicy)
>>>>>> +{
>>>>>> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>>> +	int dev_util;
>>>>>> +
>>>>>> +	if (dcc->io_interrupted) {
>>>>>> +		dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>>> +		dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
>>>>>> +		dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
>>>>>> +		return;
>>>>>> +	}
>>>>>> +
>>>>>> +	dev_util = dev_utilization(sbi);
>>>>>> +
>>>>>> +	__adjust_discard_speed(&dpolicy->min_interval,
>>>>>> +				DEF_MIN_DISCARD_ISSUE_TIME, dev_util);
>>>>>> +	__adjust_discard_speed(&dpolicy->mid_interval,
>>>>>> +				DEF_MID_DISCARD_ISSUE_TIME, dev_util);
>>>>>> +	__adjust_discard_speed(&dpolicy->max_interval,
>>>>>> +				DEF_MAX_DISCARD_ISSUE_TIME, dev_util);
>>>>>> +}
>>>>>> +
>>>>>>  static void __init_discard_policy(struct f2fs_sb_info *sbi,
>>>>>>  				struct discard_policy *dpolicy,
>>>>>>  				int discard_type, unsigned int granularity)
>>>>>> @@ -982,20 +1020,11 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
>>>>>>  	dpolicy->io_aware_gran = MAX_PLIST_NUM;
>>>>>>  
>>>>>>  	if (discard_type == DPOLICY_BG) {
>>>>>> -		dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>>> -		dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
>>>>>> -		dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
>>>>>>  		dpolicy->io_aware = true;
>>>>>>  		dpolicy->sync = false;
>>>>>>  		dpolicy->ordered = true;
>>>>>> -		if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
>>>>>> -			dpolicy->granularity = 1;
>>>>>> -			dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>>> -		}
>>>>>> +		__tune_discard_policy(sbi, dpolicy);
>>>>>>  	} else if (discard_type == DPOLICY_FORCE) {
>>>>>> -		dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>>> -		dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
>>>>>> -		dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
>>>>>>  		dpolicy->io_aware = false;
>>>>>>  	} else if (discard_type == DPOLICY_FSTRIM) {
>>>>>>  		dpolicy->io_aware = false;
>>>>>> @@ -1353,6 +1382,8 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
>>>>>>  	if (!issued && io_interrupted)
>>>>>>  		issued = -1;
>>>>>>  
>>>>>> +	dcc->io_interrupted = io_interrupted;
>>>>>> +
>>>>>>  	return issued;
>>>>>>  }
>>>>>>  
>>>>>> @@ -1370,7 +1401,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>>  		if (i + 1 < dpolicy->granularity)
>>>>>>  			break;
>>>>>>  
>>>>>> -		if (i < DEFAULT_DISCARD_GRANULARITY && dpolicy->ordered)
>>>>>> +		if (i < MID_DISCARD_GRANULARITY && dpolicy->ordered)
>>>>>>  			return __issue_discard_cmd_orderly(sbi, dpolicy);
>>>>>>  
>>>>>>  		pend_list = &dcc->pend_list[i];
>>>>>> @@ -1407,6 +1438,8 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
>>>>>>  	if (!issued && io_interrupted)
>>>>>>  		issued = -1;
>>>>>>  
>>>>>> +	dcc->io_interrupted = io_interrupted;
>>>>>> +
>>>>>>  	return issued;
>>>>>>  }
>>>>>>  
>>>>>> @@ -1576,7 +1609,11 @@ static int issue_discard_thread(void *data)
>>>>>>  	struct f2fs_sb_info *sbi = data;
>>>>>>  	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
>>>>>>  	wait_queue_head_t *q = &dcc->discard_wait_queue;
>>>>>> -	struct discard_policy dpolicy;
>>>>>> +	struct discard_policy dpolicy = {
>>>>>> +		.min_interval = DEF_MIN_DISCARD_ISSUE_TIME,
>>>>>> +		.mid_interval = DEF_MID_DISCARD_ISSUE_TIME,
>>>>>> +		.max_interval = DEF_MAX_DISCARD_ISSUE_TIME,
>>>>>> +	};
>>>>>>  	unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>>>>>>  	int issued;
>>>>>>  
>>>>>> @@ -1929,7 +1966,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>>>>  	if (!dcc)
>>>>>>  		return -ENOMEM;
>>>>>>  
>>>>>> -	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
>>>>>> +	dcc->discard_granularity = MIN_DISCARD_GRANULARITY;
>>>>>>  	INIT_LIST_HEAD(&dcc->entry_list);
>>>>>>  	for (i = 0; i < MAX_PLIST_NUM; i++)
>>>>>>  		INIT_LIST_HEAD(&dcc->pend_list[i]);
>>>>>> @@ -1945,6 +1982,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>>>>>>  	dcc->next_pos = 0;
>>>>>>  	dcc->root = RB_ROOT;
>>>>>>  	dcc->rbtree_check = false;
>>>>>> +	dcc->io_interrupted = false;
>>>>>>  
>>>>>>  	init_waitqueue_head(&dcc->discard_wait_queue);
>>>>>>  	SM_I(sbi)->dcc_info = dcc;
>>>>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>>>>>> index 422b0ceb1eaa..63b4da72cd34 100644
>>>>>> --- a/fs/f2fs/segment.h
>>>>>> +++ b/fs/f2fs/segment.h
>>>>>> @@ -616,6 +616,15 @@ static inline int utilization(struct f2fs_sb_info *sbi)
>>>>>>  					sbi->user_block_count);
>>>>>>  }
>>>>>>  
>>>>>> +static inline int dev_utilization(struct f2fs_sb_info *sbi)
>>>>>> +{
>>>>>> +	unsigned int dev_blks;
>>>>>> +
>>>>>> +	dev_blks = valid_user_blocks(sbi) + SM_I(sbi)->dcc_info->undiscard_blks;
>>>>>> +	return div_u64((u64)dev_blks * 100,
>>>>>> +			MAIN_SEGS(sbi) << sbi->log_blocks_per_seg);
>>>>>> +}
>>>>>> +
>>>>>>  /*
>>>>>>   * Sometimes f2fs may be better to drop out-of-place update policy.
>>>>>>   * And, users can control the policy through sysfs entries.
>>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>>> index b055f2ea77c5..55ed76daad23 100644
>>>>>> --- a/fs/f2fs/super.c
>>>>>> +++ b/fs/f2fs/super.c
>>>>>> @@ -2862,7 +2862,7 @@ static void f2fs_tuning_parameters(struct f2fs_sb_info *sbi)
>>>>>>  	/* adjust parameters according to the volume size */
>>>>>>  	if (sm_i->main_segments <= SMALL_VOLUME_SEGMENTS) {
>>>>>>  		F2FS_OPTION(sbi).alloc_mode = ALLOC_MODE_REUSE;
>>>>>> -		sm_i->dcc_info->discard_granularity = 1;
>>>>>> +		sm_i->dcc_info->discard_granularity = MIN_DISCARD_GRANULARITY;
>>>>>>  		sm_i->ipu_policy = 1 << F2FS_IPU_FORCE;
>>>>>>  	}
>>>>>>  
>>>>>> -- 
>>>>>> 2.18.0.rc1
>>>>>
>>>>> .
>>>>>
>>>
>>> .
>>>
> 
> .
>