On 2016/9/8 8:26, Jaegeuk Kim wrote: > On Wed, Sep 07, 2016 at 10:12:17PM +0800, Chao Yu wrote: >> On 2016/9/3 2:36, Jaegeuk Kim wrote: >>> On Fri, Sep 02, 2016 at 03:33:33PM +0800, Chao Yu wrote: >>>> Hi Jaegeuk, >>>> >>>> On 2016/8/27 8:53, Jaegeuk Kim wrote: >>>>> This can avoid bio splits due to different op_flags. >>>> >>>> I thought about this, but I think this is not a good idea to increase merging >>>> ratio of pages in bio. It breaks the rule of SYNC/ASYNC IO defined by system >>>> which indicate degree of IO emergency, finally, some/more non-emergent IO will >>>> treated as emergent one by IO scheduler, it will interrupt SYNC IOs in block >>>> layer, more seriously, it may make real SYNC IO starvation. >>> >>> I understand your concern. >>> Originally, I tried to avoid breaking a big WRITE_SYNC by a small number of >> >> Hmm.. I'm worry about the opposite case: user triggers small WRITE_SYNC IO >> periodically, meanwhile there are big number of WRITE, with our new approach, >> actually we will increase the number of synchronous WRITE IO obviously because >> we will mix ASYNC/SYNC WRITE into bio cache intensively more than before since >> we drop writepages mutexlock. So I'm afread the result is that it will mislead >> scheduling of block layer. >> >>> WRITE. And, I thought new WRITE can be piggybacked into previous WRITE_SYNC. >>> >>> IMO, this happens very occassionally since previous pending bio should be >>> WRITE_SYNC while a new request is WRITE. Even if this happens, the piggybacked >>> size would not exceed over bio's max pages. >>> If lots of WRITE come, we won't change at all. >> >> I thinks this is related to writeback / blocklayer / cgroup subsystem which use >> this tag frequently, maybe we should Cc their's mailing list for more opinion... > > Except cgroup, since we do not support it yet. :P Yeap. > > Anyway, I think we'd better verify the effect of this for a while. > For example, I'm able to write a simple program to measure fsync latency while > a bunch of buffered writes. > Meanwhile, I'll put it back to the end of dev-test repo. :) Sounds good plan. Hoping we will not suffer from regression here. ;) Thanks, > > Thanks, > >> >> What's your opinion? :) >> >> thanks, >> >>> >>> Thanks, >>> >>>> >>>> Thanks, >>>> >>>>> >>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> >>>>> --- >>>>> fs/f2fs/data.c | 5 +++++ >>>>> 1 file changed, 5 insertions(+) >>>>> >>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >>>>> index 7c8e219..c7c2022 100644 >>>>> --- a/fs/f2fs/data.c >>>>> +++ b/fs/f2fs/data.c >>>>> @@ -267,6 +267,11 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio) >>>>> >>>>> down_write(&io->io_rwsem); >>>>> >>>>> + /* WRITE can be merged into previous WRITE_SYNC */ >>>>> + if (io->bio && io->last_block_in_bio == fio->new_blkaddr - 1 && >>>>> + io->fio.op == fio->op && io->fio.op_flags == WRITE_SYNC) >>>>> + fio->op_flags = WRITE_SYNC; >>>>> + >>>>> if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 || >>>>> (io->fio.op != fio->op || io->fio.op_flags != fio->op_flags))) >>>>> __submit_merged_bio(io); >>>>> >>> >>> ------------------------------------------------------------------------------ >>> _______________________________________________ >>> Linux-f2fs-devel mailing list >>> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx >>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >>> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
