linux-kernel - [PATCH v11 1/6] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy

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Date:   Wed, 21 Dec 2022 13:58:02 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     atomlin@...mlin.com, frederic@...nel.org
Cc:     cl@...ux.com, tglx@...utronix.de, mingo@...nel.org,
        peterz@...radead.org, pauld@...hat.com, neelx@...hat.com,
        oleksandr@...alenko.name, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH v11 1/6] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy

From: Aaron Tomlin <atomlin@...mlin.com>

Introduce a CPU-specific variable namely vmstat_dirty to indicate
if a vmstat imbalance is present for a given CPU. Therefore, at
the appropriate time, we can fold all the remaining differentials.
This patch also provides trivial helpers for modification and testing.

Signed-off-by: Aaron Tomlin <atomlin@...mlin.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
---
 mm/vmstat.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c
+++ linux-2.6/mm/vmstat.c
@@ -194,6 +194,22 @@ void fold_vm_numa_events(void)
 #endif
 
 #ifdef CONFIG_SMP
+static DEFINE_PER_CPU_ALIGNED(bool, vmstat_dirty);
+
+static inline void vmstat_mark_dirty(void)
+{
+	this_cpu_write(vmstat_dirty, true);
+}
+
+static inline void vmstat_clear_dirty(void)
+{
+	this_cpu_write(vmstat_dirty, false);
+}
+
+static inline bool is_vmstat_dirty(void)
+{
+	return this_cpu_read(vmstat_dirty);
+}
 
 int calculate_pressure_threshold(struct zone *zone)
 {