MFC r281738:

MFC r281738:
Change wcommitsize default from one empirical value to another.

The new value is more predictable with growing RAM size:

        hibufspace maxvnodes      old      new
i386:
  256MB   32980992     15800  2198732  2097152
    2GB   94027776    107677   878764  4194304
amd64:
  256MB   32980992     15800  2198732  2097152
    1GB  114114560     68062  1678155  4194304
    4GB  217055232    111807  1955452  4194304
   16GB 1717846016    337308  5097465 16777216
   64GB 1734918144   1164427  1490479 16777216
  256GB 1734918144   4426453   391983 16777216

git-svn-id: svn://svn.freebsd.org/base/stable/10@282362 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f