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
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 <[email protected]>
> >>>> ---
> >>>> 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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