Re: reduce memory allocation in the btrfs direct I/O path v2

[David Sterba <dsterba@suse.cz>]

On Thu, May 12, 2022 at 12:25:57PM +0530, Anand Jain wrote:
> On 5/6/22 01:41, Christoph Hellwig wrote:
> > Hi all,
> > 
> > this series adds two minor improvements to iomap that allow btrfs
> > to avoid a memory allocation per read/write system call and another
> > one per submitted bio.  I also have at last two other pending uses
> > for the iomap functionality later on, so they are not really btrfs
> > specific either.
> > 
> > Changes since v1:
> >   - pass the private data direct to iomap_dio_rw instead of through the
> >     iocb
> >   - better document the bio_set in iomap_dio_ops
> >   - split a patch into three
> >   - use kcalloc to allocate the checksums
> > 
> > Diffstat:
> >   fs/btrfs/btrfs_inode.h |   25 --------
> >   fs/btrfs/ctree.h       |    6 -
> >   fs/btrfs/file.c        |    6 -
> >   fs/btrfs/inode.c       |  152 +++++++++++++++++++++++--------------------------
> >   fs/erofs/data.c        |    2
> >   fs/ext4/file.c         |    4 -
> >   fs/f2fs/file.c         |    4 -
> >   fs/gfs2/file.c         |    4 -
> >   fs/iomap/direct-io.c   |   26 ++++++--
> >   fs/xfs/xfs_file.c      |    6 -
> >   fs/zonefs/super.c      |    4 -
> >   include/linux/iomap.h  |   16 ++++-
> >   12 files changed, 123 insertions(+), 132 deletions(-)
> 
> This patch got me curious a couple of days back while I was tracing
> a dio read performance issue on nvme. I am sharing the results as below.
> [1]. There is no performance difference. Thx.

Thanks for the results.