On Thu, Jul 16, 2020 at 08:18:49AM -0400, Brian Foster wrote:
> Rewrite the macro as a static inline helper to clean up the logic
> and have one less macro.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_trans_space.h | 24 ++++++++++++++++--------
> fs/xfs/xfs_inode.c | 4 ++--
> fs/xfs/xfs_symlink.c | 2 +-
> 3 files changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_trans_space.h b/fs/xfs/libxfs/xfs_trans_space.h
> index c6df01a2a158..d08dfc8795c3 100644
> --- a/fs/xfs/libxfs/xfs_trans_space.h
> +++ b/fs/xfs/libxfs/xfs_trans_space.h
> @@ -55,10 +55,18 @@
> XFS_DIRENTER_MAX_SPLIT(mp,nl))
> #define XFS_DIRREMOVE_SPACE_RES(mp) \
> XFS_DAREMOVE_SPACE_RES(mp, XFS_DATA_FORK)
> -#define XFS_IALLOC_SPACE_RES(mp) \
> - (M_IGEO(mp)->ialloc_blks + \
> - ((xfs_sb_version_hasfinobt(&mp->m_sb) ? 2 : 1) * \
> - (M_IGEO(mp)->inobt_maxlevels - 1)))
> +
> +static inline int
> +xfs_ialloc_space_res(
> + struct xfs_mount *mp)
> +{
> + int res = M_IGEO(mp)->ialloc_blks;
> +
> + res += M_IGEO(mp)->inobt_maxlevels - 1;
> + if (xfs_sb_version_hasfinobt(&mp->m_sb))
> + res += M_IGEO(mp)->inobt_maxlevels - 1;
> + return res;
> +}
This misses the point I made. i.e. that the space reservation is
constant and never changes, yet we calculate it -twice- per inode
create. That means we can be calculating it hundreds of thousands of
times a second instead of just reading a variable that is likely hot
in cache.
IOWs, if we are going to improve this code, it should to be moved to
a pre-calculated, read-only, per-mount variable so the repeated
calculation goes away entirely.
Then the macro/function goes away entirely an is replaced simply
by mp->m_ialloc_space_res or M_IGEO(mp)->alloc_space_res....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
