linux-kernel - [PATCH v4 3/6] powerpc/pseries: Account for SPURR ticks on idle CPUs

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Message-Id: <1585308760-28792-4-git-send-email-ego@linux.vnet.ibm.com>
Date:   Fri, 27 Mar 2020 17:02:37 +0530
From:   "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
To:     Nathan Lynch <nathanl@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: [PATCH v4 3/6] powerpc/pseries: Account for SPURR ticks on idle CPUs

From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>

On Pseries LPARs, to calculate utilization, we need to know the
[S]PURR ticks when the CPUs were busy or idle.

Via pseries_idle_prolog(), pseries_idle_epilog(), we track the idle
PURR ticks in the VPA variable "wait_state_cycles". This patch extends
the support to account for the idle SPURR ticks. It also provides an
accessor function to accurately reads idle SPURR ticks.

Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
---
 arch/powerpc/include/asm/idle.h        | 33 +++++++++++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/setup.c |  2 ++
 2 files changed, 35 insertions(+)

diff --git a/arch/powerpc/include/asm/idle.h b/arch/powerpc/include/asm/idle.h
index d4bfb6a..accd1f5 100644
--- a/arch/powerpc/include/asm/idle.h
+++ b/arch/powerpc/include/asm/idle.h
@@ -5,13 +5,20 @@
 #include <asm/paca.h>
 
 #ifdef CONFIG_PPC_PSERIES
+DECLARE_PER_CPU(u64, idle_spurr_cycles);
 DECLARE_PER_CPU(u64, idle_entry_purr_snap);
+DECLARE_PER_CPU(u64, idle_entry_spurr_snap);
 
 static inline void snapshot_purr_idle_entry(void)
 {
 	*this_cpu_ptr(&idle_entry_purr_snap) = mfspr(SPRN_PURR);
 }
 
+static inline void snapshot_spurr_idle_entry(void)
+{
+	*this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
+}
+
 static inline void update_idle_purr_accounting(void)
 {
 	u64 wait_cycles;
@@ -22,10 +29,19 @@ static inline void update_idle_purr_accounting(void)
 	get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
 }
 
+static inline void update_idle_spurr_accounting(void)
+{
+	u64 *idle_spurr_cycles_ptr = this_cpu_ptr(&idle_spurr_cycles);
+	u64 in_spurr = *this_cpu_ptr(&idle_entry_spurr_snap);
+
+	*idle_spurr_cycles_ptr += mfspr(SPRN_SPURR) - in_spurr;
+}
+
 static inline void pseries_idle_prolog(void)
 {
 	ppc64_runlatch_off();
 	snapshot_purr_idle_entry();
+	snapshot_spurr_idle_entry();
 	/*
 	 * Indicate to the HV that we are idle. Now would be
 	 * a good time to find other work to dispatch.
@@ -36,6 +52,7 @@ static inline void pseries_idle_prolog(void)
 static inline void pseries_idle_epilog(void)
 {
 	update_idle_purr_accounting();
+	update_idle_spurr_accounting();
 	get_lppaca()->idle = 0;
 	ppc64_runlatch_on();
 }
@@ -56,5 +73,21 @@ static inline u64 read_this_idle_purr(void)
 	return be64_to_cpu(get_lppaca()->wait_state_cycles);
 }
 
+static inline u64 read_this_idle_spurr(void)
+{
+	/*
+	 * If we are reading from an idle context, update the
+	 * idle-spurr cycles corresponding to the last idle period.
+	 * Since the idle context is not yet over, take a fresh
+	 * snapshot of the idle-spurr.
+	 */
+	if (get_lppaca()->idle == 1) {
+		update_idle_spurr_accounting();
+		snapshot_spurr_idle_entry();
+	}
+
+	return *this_cpu_ptr(&idle_spurr_cycles);
+}
+
 #endif /* CONFIG_PPC_PSERIES */
 #endif
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 4905c96..1b55e80 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -318,7 +318,9 @@ static int alloc_dispatch_log_kmem_cache(void)
 }
 machine_early_initcall(pseries, alloc_dispatch_log_kmem_cache);
 
+DEFINE_PER_CPU(u64, idle_spurr_cycles);
 DEFINE_PER_CPU(u64, idle_entry_purr_snap);
+DEFINE_PER_CPU(u64, idle_entry_spurr_snap);
 static void pseries_lpar_idle(void)
 {
 	/*
-- 
1.9.4