sched_4bsd: Remove obsolete SMP scaling for ticks per priority level

The INVERSE_ESTCPU_WEIGHT scaling had been introduced by commit
b698380f33ef ("Quick fix for scaling of statclock ticks in the SMP
case. ...") to leave more discrimination room for multiple CPUs possibly
adding their ticks to the same 'struct ksegrp' (but also slightly
changing how CPU hogs are penalized).

Then, commit 8460a577a4b4 ("Make KSE a kernel option, ...") introduced
the current thread-based code, where tick accounting is only done on the
current thread, which renders this trick obsolete on !KSE.

Finally, when KSE was removed, the trick became generally obsolete.

The trick is actually even harmful because it changes the intended
behavior of priorizing more the CPUs that use the less ticks (and so,
impairs boosting "interactive" processes).

Remove it now.  Clamping of 'ts_estcpu' and its relation to the
load-average-based decay may be re-examined later.

Fixes:          8460a577a4b4 ("Make KSE a kernel option, ...")
MFC after:      2 weeks
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D57827

1 files changed, 0 insertions, 4 deletions

diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
index f86dcda218a4..98c5cd8836a8 100644
--- a/sys/kern/sched_4bsd.c
+++ b/sys/kern/sched_4bsd.c
@@ -70,11 +70,7 @@
  * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in
  * the range 100-256 Hz (approximately).
  */
-#ifdef SMP
-#define	INVERSE_ESTCPU_WEIGHT	(8 * smp_cpus)
-#else
 #define	INVERSE_ESTCPU_WEIGHT	8	/* 1 / (priorities per estcpu level). */
-#endif
 #define	NICE_WEIGHT		1	/* Priorities per nice level. */
 #define	ESTCPULIM(e)							\
 	min((e), INVERSE_ESTCPU_WEIGHT *				\