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

From: Jaegeuk Kim
Date: Tue Aug 14 2018 - 22:56:26 EST

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In reply to: Chao Yu: "Re: [PATCH 2/2] f2fs: tune discard speed with storage usage rate"
Next in thread: Chao Yu: "Re: [PATCH 2/2] f2fs: tune discard speed with storage usage rate"
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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
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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In reply to: Chao Yu: "Re: [PATCH 2/2] f2fs: tune discard speed with storage usage rate"
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