K 10
svn:author
V 3
mjg
K 8
svn:date
V 27
2019-09-16T21:37:47.816012Z
K 7
svn:log
V 662
vfs: convert struct mount counters to per-cpu

There are 3 counters modified all the time in this structure - one for
keeping the structure alive, one for preventing unmount and one for
tracking active writers. Exact values of these counters are very rarely
needed, which makes them a prime candidate for conversion to a per-cpu
scheme, resulting in much better performance.

Sample benchmark performing fstatfs (modifying 2 out of 3 counters) on
a 104-way 2 socket Skylake system:
before:   852393 ops/s
after:  76682077 ops/s

Reviewed by:	kib, jeff
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21637

END