linux-kernel - [PATCH v9 02/13] vmstat: add vmstat

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Date:	Mon, 4 Jan 2016 14:34:40 -0500
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rik van Riel" <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	<linux-kernel@...r.kernel.org>
CC:	Chris Metcalf <cmetcalf@...hip.com>
Subject: [PATCH v9 02/13] vmstat: add vmstat_idle function

This function checks to see if a vmstat worker is not running,
and the vmstat diffs don't require an update.  The function is
called from the task-isolation code to see if we need to
actually do some work to quiet vmstat.

Acked-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
---
 include/linux/vmstat.h |  2 ++
 mm/vmstat.c            | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 6f5a21993ff3..3dc82bf5bce6 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -190,6 +190,7 @@ extern void dec_zone_state(struct zone *, enum zone_stat_item);
 extern void __dec_zone_state(struct zone *, enum zone_stat_item);
 
 void quiet_vmstat(void);
+bool vmstat_idle(void);
 void cpu_vm_stats_fold(int cpu);
 void refresh_zone_stat_thresholds(void);
 
@@ -251,6 +252,7 @@ static inline void __dec_zone_page_state(struct page *page,
 static inline void refresh_zone_stat_thresholds(void) { }
 static inline void cpu_vm_stats_fold(int cpu) { }
 static inline void quiet_vmstat(void) { }
+static inline bool vmstat_idle(void) { return true; }
 
 static inline void drain_zonestat(struct zone *zone,
 			struct per_cpu_pageset *pset) { }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 0510d2ec31a6..ccc390197464 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1454,6 +1454,16 @@ static bool need_update(int cpu)
 	return false;
 }
 
+/*
+ * Report on whether vmstat processing is quiesced on the core currently:
+ * no vmstat worker running and no vmstat updates to perform.
+ */
+bool vmstat_idle(void)
+{
+	int cpu = smp_processor_id();
+	return cpumask_test_cpu(cpu, cpu_stat_off) && !need_update(cpu);
+}
+
 
 /*
  * Shepherd worker thread that checks the
-- 
2.1.2

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