[PATCH 15/23] mm: scalable bdi statistics counters.

Peter Zijlstra
2007-08-03T12:37:28Z

[-- Attachment #1: bdi_stat.patch --]
[-- Type: text/plain, Size: 4288 bytes --]

Provide scalable per backing_dev_info statistics counters.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/backing-dev.h | 85 ++++++++++++++++++++++++++++++++++++++++++--
mm/backing-dev.c | 27 +++++++++++++
2 files changed, 109 insertions(+), 3 deletions(-)

Index: linux-2.6/include/linux/backing-dev.h
===================================================================
--- linux-2.6.orig/include/linux/backing-dev.h
+++ linux-2.6/include/linux/backing-dev.h
@@ -8,6 +8,8 @@
#ifndef _LINUX_BACKING_DEV_H
#define _LINUX_BACKING_DEV_H

+#include <linux/percpu_counter.h>
+#include <linux/log2.h>
#include <asm/atomic.h>

struct page;
@@ -24,6 +26,12 @@ enum bdi_state {

typedef int (congested_fn)(void *, int);

+enum bdi_stat_item {
+ NR_BDI_STAT_ITEMS
+};
+
+#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
+
struct backing_dev_info {
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
@@ -32,15 +40,86 @@ struct backing_dev_info {
void *congested_data; /* Pointer to aux data for congested func */
void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
void *unplug_io_data;
+
+ struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
};

-static inline int bdi_init(struct backing_dev_info *bdi)
+int bdi_init(struct backing_dev_info *bdi);
+void bdi_destroy(struct backing_dev_info *bdi);
+
+static inline void __mod_bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item, s32 amount)
{
- return 0;
+ __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
}

-static inline void bdi_destroy(struct backing_dev_info *bdi)
+static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
{
+ __mod_bdi_stat(bdi, item, 1);
+}
+
+static inline void inc_bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __inc_bdi_stat(bdi, item);
+ local_irq_restore(flags);
+}
+
+static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ __mod_bdi_stat(bdi, item, -1);
+}
+
+static inline void dec_bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __dec_bdi_stat(bdi, item);
+ local_irq_restore(flags);
+}
+
+static inline s64 bdi_stat(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ return percpu_counter_read_positive(&bdi->bdi_stat[item]);
+}
+
+static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
+}
+
+static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
+ enum bdi_stat_item item)
+{
+ s64 sum;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ sum = __bdi_stat_sum(bdi, item);
+ local_irq_restore(flags);
+
+ return sum;
+}
+
+/*
+ * maximal error of a stat counter.
+ */
+static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
+{
+#ifdef CONFIG_SMP
+ return nr_cpu_ids * BDI_STAT_BATCH;
+#else
+ return 1;
+#endif
}

/*
Index: linux-2.6/mm/backing-dev.c
===================================================================
--- linux-2.6.orig/mm/backing-dev.c
+++ linux-2.6/mm/backing-dev.c
@@ -5,6 +5,33 @@
#include <linux/sched.h>
#include <linux/module.h>

+int bdi_init(struct backing_dev_info *bdi)
+{
+ int i, j;
+ int err;
+
+ for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
+ err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
+ if (err) {
+ for (j = 0; j < i; j++)
+ perpcu_counter_destroy(&bdi->bdi_stat[i]);
+ break;
+ }
+ }
+
+ return err;
+}
+EXPORT_SYMBOL(bdi_init);
+
+void bdi_destroy(struct backing_dev_info *bdi)
+{
+ int i;
+
+ for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
+ percpu_counter_destroy(&bdi->bdi_stat[i]);
+}
+EXPORT_SYMBOL(bdi_destroy);
+
static wait_queue_head_t congestion_wqh[2] = {
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])