linux-kernel - [PATCH v8 1/5] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy

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Message-Id: <20220924152227.819815-2-atomlin@redhat.com>
Date:   Sat, 24 Sep 2022 16:22:23 +0100
From:   Aaron Tomlin <atomlin@...hat.com>
To:     frederic@...nel.org, mtosatti@...hat.com
Cc:     cl@...ux.com, tglx@...utronix.de, mingo@...nel.org,
        peterz@...radead.org, pauld@...hat.com, neelx@...hat.com,
        oleksandr@...alenko.name, atomlin@...mlin.com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v8 1/5] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy

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@...hat.com>
---
 mm/vmstat.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 90af9a8572f5..24c67b2e58fd 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -195,6 +195,22 @@ 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)
 {
-- 
2.37.1