Re: [PATCHv6 0/5] iomap: Add support for per-block dirty state to improve write performance

["Andreas Grünbacher" <andreas.gruenbacher@gmail.com>]

Ritesh,

Am Mo., 5. Juni 2023 um 03:33 Uhr schrieb Ritesh Harjani (IBM)
<ritesh.list@gmail.com>:
> Hello All,
>
> Please find PATCHv6 which adds per-block dirty tracking to iomap.
> As discussed earlier this is required to improve write performance and reduce
> write amplification for cases where either blocksize is less than pagesize (such
> as Power platform with 64k pagesize) or when we have a large folio (such as xfs
> which currently supports large folio).
>
> RFCv5 -> PATCHv6:
> =================
> 1. Addresses review comments from Brian, Christoph and Matthew.
>    @Christoph:
>      - I have renamed the higher level functions such as iop_alloc/iop_free() to
>        iomap_iop_alloc/free() in v6.
>      - As for the low level bitmap accessor functions I couldn't find any better
>        naming then iop_test_/set/clear_**. I could have gone for
>        iomap_iop__test/set/clear/_** or iomap__iop_test/set/clear_**, but
>        I wasn't convinced with either of above as it also increases function
>        name.
>        Besides iop_test/set_clear_ accessors functions for uptodate and dirty
>        status tracking make sense as we are sure we have a valid iop in such
>        cases. Please do let me know if this looks ok to you.
> 2. I tried testing gfs2 (initially with no patches) with xfstests. But I always ended up
>    in some or the other deadlock (I couldn't spend any time debugging that).
>    I also ran it with -x log, but still it was always failing for me.
>    @Andreas:
>    - could you please suggest how can I test gfs2 with these patches. I see gfs2
>      can have a smaller blocksize and it uses iomap buffered io path. It will be
>      good if we can get these patches tested on it too.

here's a minimal list of tests we're running automatically on a daily basis:

https://gitlab.com/redhat/centos-stream/tests/kernel/kernel-tests/-/blob/main/filesystems/xfs/xfstests/RUNTESTS.gfs2

Please note that function inode_to_wb() in <linux/backing-dev.h>
includes some asserts that are active when CONFIG_LOCKDEP is enabled.
Those asserts will cause every single fstest to fail. So either
disable CONFIG_LOCKDEP or remove the asserts in inode_to_wb() for now.

Thanks,
Andreas

> 3. I can now say I have run some good amount of fstests on these patches on
>    these platforms and I haven't found any new failure in my testing so far.
>    arm64 (64k pagesize): with 4k -g quick
>    Power: with 4k -g auto
>    x86: 1k, 4k with -g auto and adv_auto
>
> From my testing so far these patches looks stable to me and if this looks good
> to reviewers as well, do you think this can be queued to linux-next for wider
> testing?
>
> Performance numbers copied from last patch commit message
> ==================================================
> Performance testing of below fio workload reveals ~16x performance
> improvement using nvme with XFS (4k blocksize) on Power (64K pagesize)
> FIO reported write bw scores improved from around ~28 MBps to ~452 MBps.
>
> 1. <test_randwrite.fio>
> [global]
>         ioengine=psync
>         rw=randwrite
>         overwrite=1
>         pre_read=1
>         direct=0
>         bs=4k
>         size=1G
>         dir=./
>         numjobs=8
>         fdatasync=1
>         runtime=60
>         iodepth=64
>         group_reporting=1
>
> [fio-run]
>
> 2. Also our internal performance team reported that this patch improves
>    their database workload performance by around ~83% (with XFS on Power)
>
> Ritesh Harjani (IBM) (5):
>   iomap: Rename iomap_page_create/release() to iomap_iop_alloc/free()
>   iomap: Move folio_detach_private() in iomap_iop_free() to the end
>   iomap: Refactor some iop related accessor functions
>   iomap: Allocate iop in ->write_begin() early
>   iomap: Add per-block dirty state tracking to improve performance
>
>  fs/gfs2/aops.c         |   2 +-
>  fs/iomap/buffered-io.c | 309 ++++++++++++++++++++++++++++++-----------
>  fs/xfs/xfs_aops.c      |   2 +-
>  fs/zonefs/file.c       |   2 +-
>  include/linux/iomap.h  |   1 +
>  5 files changed, 235 insertions(+), 81 deletions(-)
>
> --
> 2.40.1
>