[PATCH v3 43/46] perf/x86/intel/cmt: add CMT_UF_NOSTEAL_RMID flag

[David Carrillo-Cisneros]

Allow user to specify that rmids used by a cgroup/event cannot be stolen.

The pmonrs that are marked with CMT_UF_NOSTEAL_RMID will never lose a valid
rmid once they have receive one.

Signed-off-by: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
---
 arch/x86/events/intel/cmt.c | 10 +++++++++-
 arch/x86/events/intel/cmt.h |  5 ++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/cmt.c b/arch/x86/events/intel/cmt.c
index e677511..8cbcbc6 100644
--- a/arch/x86/events/intel/cmt.c
+++ b/arch/x86/events/intel/cmt.c
@@ -41,7 +41,7 @@ static struct monr *monr_hrchy_root;
 
 /* Flags for root monr and all its pmonrs while being monitored. */
 static enum cmt_user_flags root_monr_uflags =
-		CMT_UF_HAS_USER | CMT_UF_NOLAZY_RMID;
+		CMT_UF_HAS_USER | CMT_UF_NOSTEAL_RMID | CMT_UF_NOLAZY_RMID;
 
 /* Auxiliar flags */
 static enum cmt_user_flags *pkg_uflags_zeroes;
@@ -499,6 +499,7 @@ static void monr_dealloc(struct monr *monr)
 	 */
 	if (WARN_ON_ONCE(!(monr->flags & CMT_MONR_ZOMBIE)) ||
 	    WARN_ON_ONCE(monr->nr_has_user) ||
+	    WARN_ON_ONCE(monr->nr_nosteal_rmid) ||
 	    WARN_ON_ONCE(monr->nr_nolazy_rmid) ||
 	    WARN_ON_ONCE(monr->mon_cgrp) ||
 	    WARN_ON_ONCE(monr->mon_events))
@@ -743,10 +744,13 @@ static bool monr_account_uflags(struct monr *monr,
 
 	if (uflags & CMT_UF_HAS_USER)
 		monr->nr_has_user += account ? 1 : -1;
+	if (uflags & CMT_UF_NOSTEAL_RMID)
+		monr->nr_nosteal_rmid += account ? 1 : -1;
 	if (uflags & CMT_UF_NOLAZY_RMID)
 		monr->nr_nolazy_rmid += account ? 1 : -1;
 
 	monr->uflags =  (monr->nr_has_user ? CMT_UF_HAS_USER : 0) |
+			(monr->nr_nosteal_rmid ? CMT_UF_NOSTEAL_RMID : 0) |
 			(monr->nr_nolazy_rmid ? CMT_UF_NOLAZY_RMID : 0);
 
 	return old_flags != monr->uflags;
@@ -1400,6 +1404,10 @@ static bool can_steal_rmid(struct pmonr *pmonr)
 	u64 last_all_active, next_steal_time, last_pmonr_active;
 
 	last_all_active = atomic64_read(&monr->last_rmid_recoup);
+
+	if (pmonr_uflags(pmonr) & CMT_UF_NOSTEAL_RMID)
+		return false;
+
 	/*
 	 * Can steal if no pmonr has been stolen or all not Unused have been
 	 * in Active state for long enough.
diff --git a/arch/x86/events/intel/cmt.h b/arch/x86/events/intel/cmt.h
index 872cce0..c377076 100644
--- a/arch/x86/events/intel/cmt.h
+++ b/arch/x86/events/intel/cmt.h
@@ -290,7 +290,8 @@ enum cmt_user_flags {
 	/* if no has_user other flags are meaningless. */
 	CMT_UF_HAS_USER		= BIT(0), /* has cgroup or event users */
 	CMT_UF_NOLAZY_RMID	= BIT(1), /* try to obtain rmid on creation */
-	CMT_UF_MAX		= BIT(2) - 1,
+	CMT_UF_NOSTEAL_RMID	= BIT(2), /* do not steal this rmid */
+	CMT_UF_MAX		= BIT(3) - 1,
 	CMT_UF_ERROR		= CMT_UF_MAX + 1,
 };
 
@@ -309,6 +310,7 @@ enum cmt_user_flags {
  *			monr is monitoring in all required packages.
  * @flags:		monr_flags.
  * @nr_has_user:	nr of CMT_UF_HAS_USER set in events in mon_events.
+ * @nr_nosteal_user:	nr of CMT_UF_NOSTEAL_RMID set in events in mon_events.
  * @nr_nolazy_user:	nr of CMT_UF_NOLAZY_RMID set in events in mon_events.
  * @uflags:		monr level cmt_user_flags, or'ed with pkg_uflags.
  * @pkg_uflags:		package level cmt_user_flags, each entry is used as
@@ -335,6 +337,7 @@ struct monr {
 
 	enum monr_flags			flags;
 	int				nr_has_user;
+	int				nr_nosteal_rmid;
 	int				nr_nolazy_rmid;
 	enum cmt_user_flags		uflags;
 	enum cmt_user_flags		pkg_uflags[];
-- 
2.8.0.rc3.226.g39d4020