Re: [PATCH 0/7] Set/get accessor speedups

[Boris Burkov <boris@bur.io>]

On Tue, Jul 01, 2025 at 07:23:47PM +0200, David Sterba wrote:
> Followup to [1] bringing refactoring that allows compiler to do more
> optimizations and stack usage reduction. As the set/get helpers are
> heavily used in many functions this improves performance. I will provide
> some numbers later as I've done mostly functional tests. During the
> development I've identified a few more possible optimizations to improve
> performance, but this series is OK as is.
> 
> Overall effects of this series:
> 
> Stack:
> 
>   btrfs_set_16                                          -72 (88 -> 16)
>   btrfs_get_32                                          -56 (80 -> 24)
>   btrfs_set_8                                           -72 (88 -> 16)
>   btrfs_set_64                                          -64 (88 -> 24)
>   btrfs_get_8                                           -72 (80 -> 8)
>   btrfs_get_16                                          -64 (80 -> 16)
>   btrfs_set_32                                          -64 (88 -> 24)
>   btrfs_get_64                                          -56 (80 -> 24)
> 
>   NEW (48):
> 	  report_setget_bounds                           48
>   LOST/NEW DELTA:      +48
>   PRE/POST DELTA:     -472
> 
> Code:
> 
>      text    data     bss     dec     hex filename
>   1456601  115665   16088 1588354  183c82 pre/btrfs.ko
>   1454229  115665   16088 1585982  18333e post/btrfs.ko
> 
>   DELTA: -2372

I sent some minor inline questions / suggestions, but overall this looks
great and each patch makes a good deal of sense on its own.

Reviewed-by: Boris Burkov <boris@bur.io>

> 
> [1] https://lore.kernel.org/linux-btrfs/cover.1751032655.git.dsterba@suse.com/
> 
> David Sterba (7):
>   btrfs: accessors: simplify folio bounds checks
>   btrfs: accessors: use type sizeof constants directly
>   btrfs: accessors: inline eb bounds check and factor out the error
>     report
>   btrfs: accessors: compile-time fast path for u8
>   btrfs: accessors: compile-time fast path for u16
>   btrfs: accessors: set target address at initialization
>   btrfs: accessors: factor out split memcpy with two sources
> 
>  fs/btrfs/accessors.c | 84 +++++++++++++++++++++++++++-----------------
>  1 file changed, 51 insertions(+), 33 deletions(-)
> 
> -- 
> 2.49.0
>