[PATCH v13 10/25] fs/resctrl: Remove redundant calls to resctrl_mon_capable()

[Tony Luck]

resctrl_mon_capable() indicates whether any monitoring resources
are enabled on the system. It does this by scanning all resources.

Redundant calls to resctrl_mon_capable() in hot code paths should
be eliminated. There are two prime examples:

1) mbm_handle_overflow()
This function is called once per second from worker threads running on
each L3 domain. resctrl_mon_capable() is clearly redundant because worker
threads are only created if the MBM monitoring feature is enabled.

2) is_rmid_match()
This is called for every task on the system so making it less expensive is
appealing.  resctrl_mon_capable() is redundant because the function also
checks "r->type == RDTMON_GROUP" and this type of group can only be created
on systems that support monitoring.

Remove the call to resctrl_mon_capable() from each of these functions.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v13:
	Moved change to is_closid_match() to its own patch.
---
 fs/resctrl/monitor.c  | 2 +-
 fs/resctrl/rdtgroup.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 362737e13cd3..02e81fc82b14 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -888,7 +888,7 @@ void mbm_handle_overflow(struct work_struct *work)
 	 * If the filesystem has been unmounted this work no longer needs to
 	 * run.
 	 */
-	if (!resctrl_mounted || !resctrl_mon_capable())
+	if (!resctrl_mounted)
 		goto out_unlock;
 
 	/*
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 96a4978ce6b6..7cf809380c53 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -691,7 +691,7 @@ static bool is_closid_match(struct task_struct *t, struct rdtgroup *r)
 
 static bool is_rmid_match(struct task_struct *t, struct rdtgroup *r)
 {
-	return (resctrl_mon_capable() && (r->type == RDTMON_GROUP) &&
+	return (r->type == RDTMON_GROUP &&
 		resctrl_arch_match_rmid(t, r->mon.parent->closid,
 					r->mon.rmid));
 }
-- 
2.55.0