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Date: Tue, 14 Aug 2018 19:33:26 -0700 From: Jaegeuk Kim <jaegeuk@...nel.org> To: Chao Yu <yuchao0@...wei.com> Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, chao@...nel.org Subject: Re: [PATCH 2/2] f2fs: tune discard speed with storage usage rate 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 <yuchao0@...wei.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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