linux-kernel - [PATCH] mm,vmacache: count number of system-wide flushes

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Date:	Sun, 23 Nov 2014 18:25:55 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>
Subject: [PATCH] mm,vmacache: count number of system-wide flushes

These flushes deal with sequence number overflows, such
as for long lived threads. These are rare, but interesting
from a debugging PoV. As such, display the number of flushes
when vmacache debugging is enabled.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 include/linux/vm_event_item.h | 1 +
 mm/vmacache.c                 | 2 ++
 mm/vmstat.c                   | 1 +
 3 files changed, 4 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 730334c..9246d32 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -90,6 +90,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_DEBUG_VM_VMACACHE
 		VMACACHE_FIND_CALLS,
 		VMACACHE_FIND_HITS,
+		VMACACHE_FULL_FLUSHES,
 #endif
 		NR_VM_EVENT_ITEMS
 };
diff --git a/mm/vmacache.c b/mm/vmacache.c
index 9f25af8..b6e3662 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -17,6 +17,8 @@ void vmacache_flush_all(struct mm_struct *mm)
 {
 	struct task_struct *g, *p;
 
+	count_vm_vmacache_event(VMACACHE_FULL_FLUSHES);
+
 	/*
 	 * Single threaded tasks need not iterate the entire
 	 * list of process. We can avoid the flushing as well
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1b12d39..10d7403 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -898,6 +898,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_DEBUG_VM_VMACACHE
 	"vmacache_find_calls",
 	"vmacache_find_hits",
+	"vmacache_full_flushes",
 #endif
 #endif /* CONFIG_VM_EVENTS_COUNTERS */
 };
-- 
1.8.4.5



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