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

From: Jaegeuk Kim
Date: Tue Aug 14 2018 - 23:23:11 EST

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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?

>
> 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@xxxxxxxxxx>
> >>>>>>>> ---
> >>>>>>>> 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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