freebsd-skq/sys/fs/nullfs
Mateusz Guzik abd80ddb94 vfs: introduce v_irflag and make v_type smaller
The current vnode layout is not smp-friendly by having frequently read data
avoidably sharing cachelines with very frequently modified fields. In
particular v_iflag inspected for VI_DOOMED can be found in the same line with
v_usecount. Instead make it available in the same cacheline as the v_op, v_data
and v_type which all get read all the time.

v_type is avoidably 4 bytes while the necessary data will easily fit in 1.
Shrinking it frees up 3 bytes, 2 of which get used here to introduce a new
flag field with a new value: VIRF_DOOMED.

Reviewed by:	kib, jeff
Differential Revision:	https://reviews.freebsd.org/D22715
2019-12-08 21:30:04 +00:00
..
null_subr.c vfs: introduce v_irflag and make v_type smaller 2019-12-08 21:30:04 +00:00
null_vfsops.c vfs: introduce v_irflag and make v_type smaller 2019-12-08 21:30:04 +00:00
null_vnops.c vfs: introduce v_irflag and make v_type smaller 2019-12-08 21:30:04 +00:00
null.h sys: further adoption of SPDX licensing ID tags. 2017-11-20 19:43:44 +00:00