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Date:   Sun, 8 Mar 2020 03:46:07 +0000
From:   Alex Belits <abelits@...vell.com>
To:     "frederic@...nel.org" <frederic@...nel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>
CC:     "mingo@...nel.org" <mingo@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prasun Kapoor <pkapoor@...vell.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "will@...nel.org" <will@...nel.org>
Subject: [PATCH v2 02/12] task_isolation: vmstat: add vmstat_idle function

From: Chris Metcalf <cmetcalf@...lanox.com>

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.

Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
Signed-off-by: Alex Belits <abelits@...vell.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 2bc5e85f2514..66d9ae32cf07 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -271,6 +271,7 @@ extern void __dec_node_state(struct pglist_data *,
enum node_stat_item);
 
 void quiet_vmstat(void);
 void quiet_vmstat_sync(void);
+bool vmstat_idle(void);
 void cpu_vm_stats_fold(int cpu);
 void refresh_zone_stat_thresholds(void);
 
@@ -374,6 +375,7 @@ 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 void quiet_vmstat_sync(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 1fa0b2d04afa..5c4aec651062 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1879,6 +1879,16 @@ void quiet_vmstat_sync(void)
 	refresh_cpu_vm_stats(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)
+{
+	return !delayed_work_pending(this_cpu_ptr(&vmstat_work)) &&
+		!need_update(smp_processor_id());
+}
+
 /*
  * Shepherd worker thread that checks the
  * differentials of processors that have their worker
-- 
2.20.1

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