Re: [f2fs-dev] [PATCH 2/2] f2fs: tune discard speed with storage usage rate

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 08/16, Chao Yu wrote:
> On 2018/8/16 9:23, Jaegeuk Kim wrote:
> > On 08/15, Ju Hyung Park wrote:
> >> btrfs also distinguishes high/low end SSDs with mount option "ssd" and
> >> "ssd_spread".
> >> I believe there is no implementation inside btrfs to do it automatically.
> >>
> >> Providing users an option with a well made documentation is acceptable imo.
> > 
> > Yeah, I was thinking about this as well. How about adding "-o disk=%s" where
> > %s can be ufs/emmc/ssd/low_ssd/nvme/...?
> 
> Agreed,
> 
> > And, we also can decide the device type automatically w/ kmsg by default.
> 
> You mean by scanning kmsg to see the device type?

No, I was seeking for a way to find in block device structure, if exists.

> 
> Thanks,
> 
> > 
> >>
> >> And I personally think, if the default goes to a dynamically deciding
> >> method, it should tell it to kmsg.
> >>
> >> Thanks,
> >>
> >> On Wed, Aug 15, 2018, 12:31 PM Chao Yu <yuchao0@huawei.com> wrote:
> >>
> >>> On 2018/8/15 11:20, Jaegeuk Kim wrote:
> >>>> On 08/15, Chao Yu wrote:
> >>>>> On 2018/8/15 10:56, Jaegeuk Kim wrote:
> >>>>>> On 08/15, Chao Yu wrote:
> >>>>>>> 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?
> >>>>>>
> >>>>>> Yes, that's current condition to judge it. If there is any other
> >>> method, it'd be
> >>>>>
> >>>>> That would be hard code...
> >>>>>
> >>>>> Still I have not got any other method to do the judgment except
> >>> capacity.
> >>>>
> >>>> Maybe ufs or emmc?
> >>>
> >>> Yeah, that's may be a good way.
> >>>
> >>> I remember very initial version UFS has very poor discard performance, for
> >>> that
> >>> kind of storage, it will be not accurate?
> >>>
> >>> Let me check whether there is a flag to distinguish ufs/emmc.
> >>>
> >>> Thanks,
> >>>
> >>>>
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>>> better to change it.
> >>>>>>
> >>>>>>>
> >>>>>>> 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
> >>>>>>>>>>>>
> >>>>>>>>>>>> .
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> .
> >>>>>>>>>>
> >>>>>>>>
> >>>>>>>> .
> >>>>>>>>
> >>>>>>
> >>>>>> .
> >>>>>>
> >>>>
> >>>> .
> >>>>
> >>>
> >>>
> >>>
> >>> ------------------------------------------------------------------------------
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> >>>
> > 
> > .
> >