On 2017/8/15 11:45, Jaegeuk Kim wrote: > On 08/07, Chao Yu wrote: >> From: Chao Yu <[email protected]> >> >> Commit d618ebaf0aa8 ("f2fs: enable small discard by default") enables >> f2fs to issue 4K size discard in real-time discard mode. However, issuing >> smaller discard may cost more lifetime but releasing less free space in >> flash device. Since f2fs has ability of separating hot/cold data and >> garbage collection, we can expect that small-sized invalid region would >> expand soon with OPU, deletion or garbage collection on valid datas, so >> it's better to delay or skip issuing smaller size discards, it could help >> to reduce overmuch consumption of IO bandwidth and lifetime of flash >> storage. >> >> This patch makes f2fs selectng 64K size as its default minimal >> granularity, and issue discard with the size which is not smaller than >> minimal granularity. Also it exposes discard granularity as sysfs entry >> for configuration in different scenario. > > Hi Chao, > > I'd like to change the default value to 1 in order to keep the original > behavior, since we must avoid performance fluctuation after this single > patch. Instead, you probably can change the value through sysfs.
As I know, in fragmented filesystem space, there are may dozens of thousand discard, in scenario of cellphone user are using, 30% is above 64K size, but occupy 75% space of all undiscard space, so I changed discard_granularity to 64K just to release bulk space in device. For other small-sized discards, I expect that they may extend and cross the granularity threshold soon, and fstrim of android could cover them in the night. Do you encounter performance degression due to holding 64k-below size discard? thank, > > Thanks, > >> >> Signed-off-by: Chao Yu <[email protected]> >> --- >> v4: minor change in commit log. >> Documentation/ABI/testing/sysfs-fs-f2fs | 9 +++++++++ >> fs/f2fs/f2fs.h | 4 ++++ >> fs/f2fs/segment.c | 23 ++++++++++++++++++++++- >> fs/f2fs/sysfs.c | 7 +++++++ >> 4 files changed, 42 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs >> b/Documentation/ABI/testing/sysfs-fs-f2fs >> index 84c606fb3ca4..c579ce5e0ef5 100644 >> --- a/Documentation/ABI/testing/sysfs-fs-f2fs >> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs >> @@ -57,6 +57,15 @@ Contact: "Jaegeuk Kim" <[email protected]> >> Description: >> Controls the issue rate of small discard commands. >> >> +What: /sys/fs/f2fs/<disk>/discard_granularity >> +Date: July 2017 >> +Contact: "Chao Yu" <[email protected]> >> +Description: >> + Controls discard granularity of inner discard thread, inner >> thread >> + will not issue discards with size that is smaller than >> granularity. >> + The unit size is one block, now only support configuring in >> range >> + of [1, 512]. >> + >> What: /sys/fs/f2fs/<disk>/max_victim_search >> Date: January 2014 >> Contact: "Jaegeuk Kim" <[email protected]> >> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >> index 0ccccbfdeeab..1bcaa93bfed7 100644 >> --- a/fs/f2fs/f2fs.h >> +++ b/fs/f2fs/f2fs.h >> @@ -195,6 +195,9 @@ struct discard_entry { >> unsigned char discard_map[SIT_VBLOCK_MAP_SIZE]; /* segment discard >> bitmap */ >> }; >> >> +/* default discard granularity of inner discard thread, unit: block count */ >> +#define DEFAULT_DISCARD_GRANULARITY 16 >> + >> /* max discard pend list number */ >> #define MAX_PLIST_NUM 512 >> #define plist_idx(blk_num) ((blk_num) >= MAX_PLIST_NUM ? \ >> @@ -240,6 +243,7 @@ struct discard_cmd_control { >> struct mutex cmd_lock; >> unsigned int nr_discards; /* # of discards in the list */ >> unsigned int max_discards; /* max. discards to be issued */ >> + unsigned int discard_granularity; /* discard granularity */ >> unsigned int undiscard_blks; /* # of undiscard blocks */ >> atomic_t issued_discard; /* # of issued discard */ >> atomic_t issing_discard; /* # of issing discard */ >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >> index 71c2e0ac13d7..f336f8c541f0 100644 >> --- a/fs/f2fs/segment.c >> +++ b/fs/f2fs/segment.c >> @@ -1019,7 +1019,8 @@ static void __issue_discard_cmd(struct f2fs_sb_info >> *sbi, bool issue_cond) >> f2fs_bug_on(sbi, >> !__check_rb_tree_consistence(sbi, &dcc->root)); >> blk_start_plug(&plug); >> - for (i = MAX_PLIST_NUM - 1; i >= 0; i--) { >> + for (i = MAX_PLIST_NUM - 1; i >= 0 && >> + i >= dcc->discard_granularity - 1; i--) { >> pend_list = &dcc->pend_list[i]; >> list_for_each_entry_safe(dc, tmp, pend_list, list) { >> f2fs_bug_on(sbi, dc->state != D_PREP); >> @@ -1035,6 +1036,24 @@ static void __issue_discard_cmd(struct f2fs_sb_info >> *sbi, bool issue_cond) >> mutex_unlock(&dcc->cmd_lock); >> } >> >> +static void __drop_discard_cmd(struct f2fs_sb_info *sbi) >> +{ >> + struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info; >> + struct list_head *pend_list; >> + struct discard_cmd *dc, *tmp; >> + int i; >> + >> + mutex_lock(&dcc->cmd_lock); >> + for (i = MAX_PLIST_NUM - 1; i >= 0; i--) { >> + pend_list = &dcc->pend_list[i]; >> + list_for_each_entry_safe(dc, tmp, pend_list, list) { >> + f2fs_bug_on(sbi, dc->state != D_PREP); >> + __remove_discard_cmd(sbi, dc); >> + } >> + } >> + mutex_unlock(&dcc->cmd_lock); >> +} >> + >> static void __wait_one_discard_bio(struct f2fs_sb_info *sbi, >> struct discard_cmd *dc) >> { >> @@ -1117,6 +1136,7 @@ void stop_discard_thread(struct f2fs_sb_info *sbi) >> void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi) >> { >> __issue_discard_cmd(sbi, false); >> + __drop_discard_cmd(sbi); >> __wait_discard_cmd(sbi, false); >> } >> >> @@ -1449,6 +1469,7 @@ static int create_discard_cmd_control(struct >> f2fs_sb_info *sbi) >> atomic_set(&dcc->discard_cmd_cnt, 0); >> dcc->nr_discards = 0; >> dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg; >> + dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY; >> dcc->undiscard_blks = 0; >> dcc->root = RB_ROOT; >> >> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c >> index 045b948c7466..4e5a95e9e666 100644 >> --- a/fs/f2fs/sysfs.c >> +++ b/fs/f2fs/sysfs.c >> @@ -152,6 +152,11 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, >> spin_unlock(&sbi->stat_lock); >> return count; >> } >> + >> + if (!strcmp(a->attr.name, "discard_granularity") && >> + (t == 0 || t > MAX_PLIST_NUM)) >> + return -EINVAL; >> + >> *ui = t; >> >> if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0) >> @@ -241,6 +246,7 @@ F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, >> gc_no_gc_sleep_time, no_gc_sleep_time); >> F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_idle, gc_idle); >> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments); >> F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, >> max_discards); >> +F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, >> discard_granularity); >> F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, >> reserved_blocks); >> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections); >> F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy); >> @@ -281,6 +287,7 @@ static struct attribute *f2fs_attrs[] = { >> ATTR_LIST(gc_idle), >> ATTR_LIST(reclaim_segments), >> ATTR_LIST(max_small_discards), >> + ATTR_LIST(discard_granularity), >> ATTR_LIST(batched_trim_sections), >> ATTR_LIST(ipu_policy), >> ATTR_LIST(min_ipu_util), >> -- >> 2.14.0 > > . > ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
