linux-kernel - [PATCH-tip v2 09/10] locking/lock_events: Don't show pvqspinlock events on bare metal

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Message-Id: <1550263810-31947-10-git-send-email-longman@redhat.com>
Date:   Fri, 15 Feb 2019 15:50:09 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH-tip v2 09/10] locking/lock_events: Don't show pvqspinlock events on bare metal

On bare metail, the pvqspinlock event counts will always be 0. So there
is no point in showing their corresponding debugfs files. So they are
skipped in this case.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/locking/lock_events.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/lock_events.c b/kernel/locking/lock_events.c
index 71c36d1..fa2c2f9 100644
--- a/kernel/locking/lock_events.c
+++ b/kernel/locking/lock_events.c
@@ -115,6 +115,29 @@ static ssize_t lockevent_write(struct file *file, const char __user *user_buf,
 	.llseek = default_llseek,
 };
 
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+#include <asm/paravirt.h>
+
+static bool __init skip_lockevent(const char *name)
+{
+	static int pv_on __initdata = -1;
+
+	if (pv_on < 0)
+		pv_on = !pv_is_native_spin_unlock();
+	/*
+	 * Skip PV qspinlock events on bare metal.
+	 */
+	if (!pv_on && !memcmp(name, "pv_", 3))
+		return true;
+	return false;
+}
+#else
+static inline bool skip_lockevent(const char *name)
+{
+	return false;
+}
+#endif
+
 /*
  * Initialize debugfs for the locking event counts.
  */
@@ -133,10 +156,13 @@ static int __init init_lockevent_counts(void)
 	 * root is allowed to do the read/write to limit impact to system
 	 * performance.
 	 */
-	for (i = 0; i < lockevent_num; i++)
+	for (i = 0; i < lockevent_num; i++) {
+		if (skip_lockevent(lockevent_names[i]))
+			continue;
 		if (!debugfs_create_file(lockevent_names[i], 0400, d_counts,
 					 (void *)(long)i, &fops_lockevent))
 			goto fail_undo;
+	}
 
 	if (!debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200,
 				 d_counts, (void *)(long)LOCKEVENT_reset_cnts,
-- 
1.8.3.1