[PATCH TAKE 2 5/6] reduce imaxpct for big filesystems,

[xaiki@xxxxxxx]

From: Niv Sardi <xaiki@xxxxxxx>

imaxpct is set to 25% (XFS_DFL_IMAXIMUM_PCT) for FS < 1 TB,
then 5% for FS < 50 TB,
and then (over 50 TB) 1%.

It is implemented as a simple step function in calc_default_imaxpct()
---
 xfsprogs/mkfs/xfs_mkfs.c |   27 +++++++++++++++++++++++++--
 1 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/xfsprogs/mkfs/xfs_mkfs.c b/xfsprogs/mkfs/xfs_mkfs.c
index 3689eb7..a8af6e2 100644
--- a/xfsprogs/mkfs/xfs_mkfs.c
+++ b/xfsprogs/mkfs/xfs_mkfs.c
@@ -374,6 +374,29 @@ validate_log_size(__uint64_t logblocks, int blocklog, int 
min_logblocks)
        }
 }
 
+static int
+calc_default_imaxpct(
+       int             blocklog,
+       __uint64_t      dblocks)
+{
+       /*
+        * This returns the % of the disk space that is used for
+        * inodes, it changes relatively to the FS size:
+        *  - over  50 TB, use 1%,
+        *  - 1TB - 50 TB, use 5%,
+        *  - under  1 TB, use XFS_DFL_IMAXIMUM_PCT (25%).
+        */
+
+       if (dblocks < TERABYTES(1, blocklog)) {
+               return XFS_DFL_IMAXIMUM_PCT;
+       } else if (dblocks < TERABYTES(50, blocklog)) {
+               return 5;
+       }
+
+       return 1;
+}
+
+
 void
 calc_default_ag_geometry(
        int             blocklog,
@@ -1986,7 +2009,7 @@ an AG size that is one stripe unit smaller, for example 
%llu.\n"),
                        dfile, isize, (long long)agcount, (long long)agsize,
                        "", sectorsize, attrversion,
                        "", blocksize, (long long)dblocks,
-                               imflag ? imaxpct : XFS_DFL_IMAXIMUM_PCT,
+                              calc_default_imaxpct(blocklog, dblocks),
                        "", dsunit, dswidth,
                        dirversion, dirversion == 1 ? blocksize : dirblocksize,
                        logfile, 1 << blocklog, (long long)logblocks,
@@ -2023,7 +2046,7 @@ an AG size that is one stripe unit smaller, for example 
%llu.\n"),
                (__uint8_t)(rtextents ?
                        libxfs_highbit32((unsigned int)rtextents) : 0);
        sbp->sb_inprogress = 1; /* mkfs is in progress */
-       sbp->sb_imax_pct = imflag ? imaxpct : XFS_DFL_IMAXIMUM_PCT;
+       sbp->sb_imax_pct = calc_default_imaxpct(blocklog, dblocks);
        sbp->sb_icount = 0;
        sbp->sb_ifree = 0;
        sbp->sb_fdblocks = dblocks - agcount * XFS_PREALLOC_BLOCKS(mp) -
-- 
1.5.3.5