staging: zcache: introduce zero-filled page stat count

Introduce zero-filled page statistics to monitor the number of
zero-filled pages.
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/zcache/debug.c

@@ -35,6 +35,8 @@ ssize_t zcache_pers_ate_eph;
 ssize_t zcache_pers_ate_eph_failed;
 ssize_t zcache_evicted_eph_zpages;
 ssize_t zcache_evicted_eph_pageframes;
+ssize_t zcache_zero_filled_pages;
+ssize_t zcache_zero_filled_pages_max;
 
 #define ATTR(x)  { .name = #x, .val = &zcache_##x, }
 static struct debug_entry {
@@ -62,6 +64,7 @@ static struct debug_entry {
 	ATTR(last_inactive_anon_pageframes),
 	ATTR(eph_nonactive_puts_ignored),
 	ATTR(pers_nonactive_puts_ignored),
+	ATTR(zero_filled_pages),
 #ifdef CONFIG_ZCACHE_WRITEBACK
 	ATTR(outstanding_writeback_pages),
 	ATTR(writtenback_pages),

drivers/staging/zcache/debug.h

@@ -122,6 +122,21 @@ static inline void dec_zcache_pers_zpages(unsigned zpages)
 	zcache_pers_zpages = atomic_sub_return(zpages, &zcache_pers_zpages_atomic);
 }
 
+extern ssize_t zcache_zero_filled_pages;
+static atomic_t zcache_zero_filled_pages_atomic = ATOMIC_INIT(0);
+extern ssize_t zcache_zero_filled_pages_max;
+static inline void inc_zcache_zero_filled_pages(void)
+{
+	zcache_zero_filled_pages = atomic_inc_return(
+					&zcache_zero_filled_pages_atomic);
+	if (zcache_zero_filled_pages > zcache_zero_filled_pages_max)
+		zcache_zero_filled_pages_max = zcache_zero_filled_pages;
+}
+static inline void dec_zcache_zero_filled_pages(void)
+{
+	zcache_zero_filled_pages = atomic_dec_return(
+					&zcache_zero_filled_pages_atomic);
+}
 static inline unsigned long curr_pageframes_count(void)
 {
 	return zcache_pageframes_alloced -
@@ -200,6 +215,8 @@ static inline void inc_zcache_eph_zpages(void) { };
 static inline void dec_zcache_eph_zpages(unsigned zpages) { };
 static inline void inc_zcache_pers_zpages(void) { };
 static inline void dec_zcache_pers_zpages(unsigned zpages) { };
+static inline void inc_zcache_zero_filled_pages(void) { };
+static inline void dec_zcache_zero_filled_pages(void) { };
 static inline unsigned long curr_pageframes_count(void)
 {
 	return 0;

drivers/staging/zcache/zcache-main.c

@@ -374,6 +374,7 @@ static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
 	if (page_is_zero_filled(page)) {
 		clen = 0;
 		zero_filled = true;
+		inc_zcache_zero_filled_pages();
 		goto got_pampd;
 	}
 
@@ -440,6 +441,7 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
 	if (page_is_zero_filled(page)) {
 		clen = 0;
 		zero_filled = true;
+		inc_zcache_zero_filled_pages();
 		goto got_pampd;
 	}
 
@@ -652,6 +654,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
 		zpages = 1;
 		if (!raw)
 			*sizep = PAGE_SIZE;
+		dec_zcache_zero_filled_pages();
 		goto zero_fill;
 	}
 
@@ -702,6 +705,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
 		zero_filled = true;
 		zsize = 0;
 		zpages = 1;
+		dec_zcache_zero_filled_pages();
 	}
 
 	if (pampd_is_remote(pampd) && !zero_filled) {