[PATCH v2 01/12] task_isolation: vmstat: add quiet_vmstat_sync function

Alex Belits
2020-03-08T03:44:44Z

From: Chris Metcalf <cmetcalf@mellanox.com>

In commit f01f17d3705b ("mm, vmstat: make quiet_vmstat lighter")
the quiet_vmstat() function became asynchronous, in the sense that
the vmstat work was still scheduled to run on the core when the
function returned. For task isolation, we need a synchronous
version of the function that guarantees that the vmstat worker
will not run on the core on return from the function. Add a
quiet_vmstat_sync() function with that semantic.

Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
Signed-off-by: Alex Belits <abelits@marvell.com>
---
include/linux/vmstat.h | 2 ++
mm/vmstat.c | 9 +++++++++
2 files changed, 11 insertions(+)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 292485f3d24d..2bc5e85f2514 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -270,6 +270,7 @@ extern void __dec_zone_state(struct zone *, enum zone_stat_item);
extern void __dec_node_state(struct pglist_data *, enum node_stat_item);

void quiet_vmstat(void);
+void quiet_vmstat_sync(void);
void cpu_vm_stats_fold(int cpu);
void refresh_zone_stat_thresholds(void);

@@ -372,6 +373,7 @@ static inline void __dec_node_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 void quiet_vmstat_sync(void) { }

static inline void drain_zonestat(struct zone *zone,
struct per_cpu_pageset *pset) { }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 78d53378db99..1fa0b2d04afa 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1870,6 +1870,15 @@ void quiet_vmstat(void)
refresh_cpu_vm_stats(false);
}

+/*
+ * Synchronously quiet vmstat so the work is guaranteed not to run on return.
+ */
+void quiet_vmstat_sync(void)
+{
+ cancel_delayed_work_sync(this_cpu_ptr(&vmstat_work));
+ refresh_cpu_vm_stats(false);
+}
+
/*
* Shepherd worker thread that checks the
* differentials of processors that have their worker