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 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. :) 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
