Re: [PATCH v5 00/11] simplify block layer based on immutable biovecs

Ming Lin
2015-07-13T05:12:40Z

On Mon, 2015-07-06 at 00:11 -0700, mlin@kernel.org wrote:
> Hi Mike,
>
> On Wed, 2015-06-10 at 17:46 -0400, Mike Snitzer wrote:
> > I've been busy getting DM changes for the 4.2 merge window finalized.
> > As such I haven't connected with others on the team to discuss this
> > issue.
> >
> > I'll see if we can make time in the next 2 days. But I also have
> > RHEL-specific kernel deadlines I'm coming up against.
> >
> > Seems late to be staging this extensive a change for 4.2... are you
> > pushing for this code to land in the 4.2 merge window? Or do we have
> > time to work this further and target the 4.3 merge?
> >
>
> 4.2-rc1 was out.
> Would you have time to work together for 4.3 merge?

Ping ...

What can I do to move forward?

This patchset not only simplify block layer a lot, it's also a
prerequisite of the direct IO rewrite patches, which I saw 40%
performance improvement for null_blk and 10% improvement for NVMe
drives. I have been fixing bugs for the direct IO patches. I'll post it
once it passes xfstests.

Mike,
Can I have your ACK? Or do you have other test plan?

Thanks,
Ming

>
> Fio test results(4.1-rc4/rc7) showed no performance regressions
> for HW/SW RAID6 and DM stripe tests.
> http://minggr.net/pub/20150608/fio_results/summary.log
>
> v5:
> - rebase on top of 4.2-rc1
> - reorder patch 6,7
> - add NeilBrown's ACKs
> - fix memory leak: free "bio_split" bioset in blk_release_queue()
>
> v4:
> - rebase on top of 4.1-rc4
> - use BIO_POOL_SIZE instead of number 4 for bioset_create()
> - call blk_queue_split() in blk_mq_make_request()
> - call blk_queue_split() in zram_make_request()
> - add patch "block: remove bio_get_nr_vecs()"
> - remove split code in blkdev_issue_discard()
> - drop patch "md/raid10: make sync_request_write() call bio_copy_data()".
> NeilBrown queued it.
> - drop patch "block: allow __blk_queue_bounce() to handle bios larger than BIO_MAX_PAGES".
> Will send it seperately
>
> v3:
> - rebase on top of 4.1-rc2
> - support for QUEUE_FLAG_SG_GAPS
> - update commit logs of patch 2&4
> - split bio for chunk_aligned_read
>
> v2: https://lkml.org/lkml/2015/4/28/28
> v1: https://lkml.org/lkml/2014/12/22/128
>
> This is the 5th attempt of simplifying block layer based on immutable
> biovecs. Immutable biovecs, implemented by Kent Overstreet, have been
> available in mainline since v3.14. Its original goal was actually making
> generic_make_request() accept arbitrarily sized bios, and pushing the
> splitting down to the drivers or wherever it's required. See also
> discussions in the past, [1] [2] [3].
>
> This will bring not only performance improvements, but also a great amount
> of reduction in code complexity all over the block layer. Performance gain
> is possible due to the fact that bio_add_page() does not have to check
> unnecesary conditions such as queue limits or if biovecs are mergeable.
> Those will be delegated to the driver level. Kent already said that he
> actually benchmarked the impact of this with fio on a micron p320h, which
> showed definitely a positive impact.
>
> Moreover, this patchset also allows a lot of code to be deleted, mainly
> because of removal of merge_bvec_fn() callbacks. We have been aware that
> it has been always a delicate issue for stacking block drivers (e.g. md
> and bcache) to handle merging bio consistently. This simplication will
> help every individual block driver avoid having such an issue.
>
> Patches are against 4.2-rc1. These are also available in my git repo at:
>
> https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=block-generic-req
> git://git.kernel.org/pub/scm/linux/kernel/git/mlin/linux.git block-generic-req
>
> This patchset is a prerequisite of other consecutive patchsets, e.g.
> multipage biovecs, rewriting plugging, or rewriting direct-IO, which are
> excluded this time. That means, this patchset should not bring any
> regression to end-users.
>
> Comments are welcome.
> Ming
>
> [1] https://lkml.org/lkml/2014/11/23/263
> [2] https://lkml.org/lkml/2013/11/25/732
> [3] https://lkml.org/lkml/2014/2/26/618
>
> Dongsu Park (1):
> Documentation: update notes in biovecs about arbitrarily sized bios
>
> Kent Overstreet (8):
> block: make generic_make_request handle arbitrarily sized bios
> block: simplify bio_add_page()
> bcache: remove driver private bio splitting code
> btrfs: remove bio splitting and merge_bvec_fn() calls
> md/raid5: get rid of bio_fits_rdev()
> block: kill merge_bvec_fn() completely
> fs: use helper bio_add_page() instead of open coding on bi_io_vec
> block: remove bio_get_nr_vecs()
>
> Ming Lin (2):
> block: remove split code in blkdev_issue_discard
> md/raid5: split bio for chunk_aligned_read
>
> Documentation/block/biovecs.txt | 10 +-
> block/bio.c | 152 ++++++++++------------------
> block/blk-core.c | 19 ++--
> block/blk-lib.c | 73 +++----------
> block/blk-merge.c | 148 +++++++++++++++++++++++++--
> block/blk-mq.c | 4 +
> block/blk-settings.c | 22 ----
> block/blk-sysfs.c | 3 +
> drivers/block/drbd/drbd_int.h | 1 -
> drivers/block/drbd/drbd_main.c | 1 -
> drivers/block/drbd/drbd_req.c | 37 +------
> drivers/block/pktcdvd.c | 27 +----
> drivers/block/ps3vram.c | 2 +
> drivers/block/rbd.c | 47 ---------
> drivers/block/rsxx/dev.c | 2 +
> drivers/block/umem.c | 2 +
> drivers/block/zram/zram_drv.c | 2 +
> drivers/md/bcache/bcache.h | 18 ----
> drivers/md/bcache/io.c | 100 +-----------------
> drivers/md/bcache/journal.c | 4 +-
> drivers/md/bcache/request.c | 16 +--
> drivers/md/bcache/super.c | 32 +-----
> drivers/md/bcache/util.h | 5 +-
> drivers/md/bcache/writeback.c | 4 +-
> drivers/md/dm-cache-target.c | 21 ----
> drivers/md/dm-crypt.c | 16 ---
> drivers/md/dm-era-target.c | 15 ---
> drivers/md/dm-flakey.c | 16 ---
> drivers/md/dm-io.c | 2 +-
> drivers/md/dm-linear.c | 16 ---
> drivers/md/dm-log-writes.c | 16 ---
> drivers/md/dm-raid.c | 19 ----
> drivers/md/dm-snap.c | 15 ---
> drivers/md/dm-stripe.c | 21 ----
> drivers/md/dm-table.c | 8 --
> drivers/md/dm-thin.c | 31 ------
> drivers/md/dm-verity.c | 16 ---
> drivers/md/dm.c | 129 +----------------------
> drivers/md/dm.h | 2 -
> drivers/md/linear.c | 43 --------
> drivers/md/md.c | 28 +----
> drivers/md/md.h | 12 ---
> drivers/md/multipath.c | 21 ----
> drivers/md/raid0.c | 56 ----------
> drivers/md/raid0.h | 2 -
> drivers/md/raid1.c | 58 +----------
> drivers/md/raid10.c | 121 +---------------------
> drivers/md/raid5.c | 92 ++++++-----------
> drivers/s390/block/dcssblk.c | 2 +
> drivers/s390/block/xpram.c | 2 +
> drivers/staging/lustre/lustre/llite/lloop.c | 2 +
> fs/btrfs/compression.c | 5 +-
> fs/btrfs/extent_io.c | 9 +-
> fs/btrfs/inode.c | 3 +-
> fs/btrfs/scrub.c | 18 +---
> fs/btrfs/volumes.c | 72 -------------
> fs/buffer.c | 7 +-
> fs/direct-io.c | 2 +-
> fs/ext4/page-io.c | 3 +-
> fs/ext4/readpage.c | 2 +-
> fs/f2fs/data.c | 2 +-
> fs/gfs2/lops.c | 9 +-
> fs/jfs/jfs_logmgr.c | 14 +--
> fs/logfs/dev_bdev.c | 4 +-
> fs/mpage.c | 4 +-
> fs/nilfs2/segbuf.c | 2 +-
> fs/xfs/xfs_aops.c | 3 +-
> include/linux/bio.h | 1 -
> include/linux/blkdev.h | 13 +--
> include/linux/device-mapper.h | 4 -
> mm/page_io.c | 8 +-
> 71 files changed, 340 insertions(+), 1358 deletions(-)