On 2020/2/25 5:53, Jaegeuk Kim wrote: > On 02/19, Chao Yu wrote: >> On 2020/2/19 11:04, Jaegeuk Kim wrote: >>> On 02/19, Chao Yu wrote: >>>> On 2020/2/19 7:27, Jaegeuk Kim wrote: >>>>> On 02/17, Chao Yu wrote: >>>>>> On 2020/2/15 2:58, Jaegeuk Kim wrote: >>>>>>> FG_GC needs to move entire section more quickly. >>>>>>> >>>>>>> Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org> >>>>>>> --- >>>>>>> fs/f2fs/gc.c | 2 +- >>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>>>> index bbf4db3f6bb4..1676eebc8c8b 100644 >>>>>>> --- a/fs/f2fs/gc.c >>>>>>> +++ b/fs/f2fs/gc.c >>>>>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info >>>>>>> *sbi, >>>>>>> >>>>>>> if (get_valid_blocks(sbi, segno, false) == 0) >>>>>>> goto freed; >>>>>>> - if (__is_large_section(sbi) && >>>>>>> + if (gc_type == BG_GC && __is_large_section(sbi) && >>>>>>> migrated >= sbi->migration_granularity) >>>>>> >>>>>> I knew migrating one large section is a more efficient way, but this can >>>>>> increase long-tail latency of f2fs_balance_fs() occasionally, especially >>>>>> in >>>>>> extreme fragmented space. >>>>> >>>>> FG_GC requires to wait for whole section migration which shows the entire >>>>> latency. >>>> >>>> That will cause long-tail latency for single f2fs_balance_fs() procedure, >>>> which it looks a very long hang when userspace call f2fs syscall, so why >>>> not splitting total elapsed time into several f2fs_balance_fs() to avoid >>>> that. >>> >>> Then, other ops can easily make more dirty segments. The intention of FG_GC >>> is >> >> Yup, that's a problem, if there are more dirty datas being made, reserved >> segments >> may be ran out during FG_GC. >> >>> to block everything and make min. free segments as a best shot. >> >> I just try to simulate write GC's logic in FTL to mitigate single op's max >> latency, >> otherwise benchmark looks hang during FG_GC (in a 500mb+ section).
Oh, if we want to FG_GC only migrate on segment on time, it needs to change has_not_enough_free_secs() condition as well, so previous logic is broken. Nvm, please add: Reviewed-by: Chao Yu <yuch...@huawei.com> > > Hmm, I think we may need to think another way like doing BG_GC more > aggressively. Agreed, I guess SMR scenario may need such policy: higher trigger frequency on bggc when free space decreases, but less block migration for each bggc cycle. Thanks, > >> >> Thanks, >> >>> >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> Thanks, >>>>>> >>>>>>> goto skip; >>>>>>> if (!PageUptodate(sum_page) || >>>>>>> unlikely(f2fs_cp_error(sbi))) >>>>>>> >>>>> . >>>>> >>> . >>> > . > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
