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SubjectRe: [patch] Make diskstats per-cpu using kmalloc_percpu
Ravikiran G Thirumalai <kiran@in.ibm.com> wrote:
>
> This version makes the disk stats on struct gendisk per-cpu.

Well OK, but it has lots of SCARY UPPER-CASE MACROS and disk_stat_inc(),
disk_stat_dec() and disk_stat_sub() can all be defined in terms of
disk_stat_add().

I did this to it:


drivers/block/genhd.c | 27 ++++++++-----
drivers/block/ll_rw_blk.c | 29 +++++++-------
drivers/md/md.c | 4 +
fs/partitions/check.c | 8 ---
include/linux/genhd.h | 94 ++++++++++++++++++++++++++++++++++++++++++----
5 files changed, 123 insertions(+), 39 deletions(-)

diff -puN drivers/block/genhd.c~per-cpu-disk-stats drivers/block/genhd.c
--- 25/drivers/block/genhd.c~per-cpu-disk-stats 2003-02-24 23:44:09.000000000 -0800
+++ 25-akpm/drivers/block/genhd.c 2003-02-24 23:50:04.000000000 -0800
@@ -318,7 +318,7 @@ static inline unsigned jiffies_to_msec(u
return (jif / HZ) * 1000 + (jif % HZ) * 1000 / HZ;
#endif
}
-static ssize_t disk_stat_read(struct gendisk * disk, char *page)
+static ssize_t disk_stats_read(struct gendisk * disk, char *page)
{
disk_round_stats(disk);
return sprintf(page,
@@ -326,14 +326,16 @@ static ssize_t disk_stat_read(struct gen
"%8u %8u %8llu %8u "
"%8u %8u %8u"
"\n",
- disk->reads, disk->read_merges,
- (unsigned long long)disk->read_sectors,
- jiffies_to_msec(disk->read_ticks),
- disk->writes, disk->write_merges,
- (unsigned long long)disk->write_sectors,
- jiffies_to_msec(disk->write_ticks),
- disk->in_flight, jiffies_to_msec(disk->io_ticks),
- jiffies_to_msec(disk->time_in_queue));
+ disk_stat_read(disk, reads), disk_stat_read(disk, read_merges),
+ (unsigned long long)disk_stat_read(disk, read_sectors),
+ jiffies_to_msec(disk_stat_read(disk, read_ticks)),
+ disk_stat_read(disk, writes),
+ disk_stat_read(disk, write_merges),
+ (unsigned long long)disk_stat_read(disk, write_sectors),
+ jiffies_to_msec(disk_stat_read(disk, write_ticks)),
+ disk_stat_read(disk, in_flight),
+ jiffies_to_msec(disk_stat_read(disk, io_ticks)),
+ jiffies_to_msec(disk_stat_read(disk, time_in_queue)));
}
static struct disk_attribute disk_attr_dev = {
.attr = {.name = "dev", .mode = S_IRUGO },
@@ -349,7 +351,7 @@ static struct disk_attribute disk_attr_s
};
static struct disk_attribute disk_attr_stat = {
.attr = {.name = "stat", .mode = S_IRUGO },
- .show = disk_stat_read
+ .show = disk_stats_read
};

static struct attribute * default_attrs[] = {
@@ -365,6 +367,7 @@ static void disk_release(struct kobject
struct gendisk *disk = to_disk(kobj);
kfree(disk->random);
kfree(disk->part);
+ free_disk_stats(disk);
kfree(disk);
}

@@ -384,6 +387,10 @@ struct gendisk *alloc_disk(int minors)
struct gendisk *disk = kmalloc(sizeof(struct gendisk), GFP_KERNEL);
if (disk) {
memset(disk, 0, sizeof(struct gendisk));
+ if (!init_disk_stats(disk)) {
+ kfree(disk);
+ return NULL;
+ }
if (minors > 1) {
int size = (minors - 1) * sizeof(struct hd_struct);
disk->part = kmalloc(size, GFP_KERNEL);
diff -puN drivers/block/ll_rw_blk.c~per-cpu-disk-stats drivers/block/ll_rw_blk.c
--- 25/drivers/block/ll_rw_blk.c~per-cpu-disk-stats 2003-02-24 23:44:09.000000000 -0800
+++ 25-akpm/drivers/block/ll_rw_blk.c 2003-02-24 23:44:09.000000000 -0800
@@ -1458,17 +1458,17 @@ void drive_stat_acct(struct request *rq,
return;

if (rw == READ) {
- rq->rq_disk->read_sectors += nr_sectors;
+ disk_stat_add(rq->rq_disk, read_sectors, nr_sectors);
if (!new_io)
- rq->rq_disk->read_merges++;
+ disk_stat_inc(rq->rq_disk, read_merges);
} else if (rw == WRITE) {
- rq->rq_disk->write_sectors += nr_sectors;
+ disk_stat_add(rq->rq_disk, write_sectors, nr_sectors);
if (!new_io)
- rq->rq_disk->write_merges++;
+ disk_stat_inc(rq->rq_disk, write_merges);
}
if (new_io) {
disk_round_stats(rq->rq_disk);
- rq->rq_disk->in_flight++;
+ disk_stat_inc(rq->rq_disk, in_flight);
}
}

@@ -1508,11 +1508,12 @@ void disk_round_stats(struct gendisk *di
{
unsigned long now = jiffies;

- disk->time_in_queue += disk->in_flight * (now - disk->stamp);
+ disk_stat_add(disk, time_in_queue,
+ disk_stat_read(disk, in_flight) * (now - disk->stamp));
disk->stamp = now;

- if (disk->in_flight)
- disk->io_ticks += (now - disk->stamp_idle);
+ if (disk_stat_read(disk, in_flight))
+ disk_stat_add(disk, io_ticks, (now - disk->stamp_idle));
disk->stamp_idle = now;
}

@@ -1628,7 +1629,7 @@ static int attempt_merge(request_queue_t

if (req->rq_disk) {
disk_round_stats(req->rq_disk);
- req->rq_disk->in_flight--;
+ disk_stat_dec(req->rq_disk, in_flight);
}

__blk_put_request(q, next);
@@ -2180,16 +2181,16 @@ void end_that_request_last(struct reques
unsigned long duration = jiffies - req->start_time;
switch (rq_data_dir(req)) {
case WRITE:
- disk->writes++;
- disk->write_ticks += duration;
+ disk_stat_inc(disk, writes);
+ disk_stat_add(disk, write_ticks, duration);
break;
case READ:
- disk->reads++;
- disk->read_ticks += duration;
+ disk_stat_inc(disk, reads);
+ disk_stat_add(disk, read_ticks, duration);
break;
}
disk_round_stats(disk);
- disk->in_flight--;
+ disk_stat_dec(disk, in_flight);
}
__blk_put_request(req->q, req);
}
diff -puN drivers/md/md.c~per-cpu-disk-stats drivers/md/md.c
--- 25/drivers/md/md.c~per-cpu-disk-stats 2003-02-24 23:44:09.000000000 -0800
+++ 25-akpm/drivers/md/md.c 2003-02-24 23:44:09.000000000 -0800
@@ -2803,7 +2803,9 @@ static int is_mddev_idle(mddev_t *mddev)
idle = 1;
ITERATE_RDEV(mddev,rdev,tmp) {
struct gendisk *disk = rdev->bdev->bd_contains->bd_disk;
- curr_events = disk->read_sectors + disk->write_sectors - disk->sync_io;
+ curr_events = disk_stat_read(disk, read_sectors) +
+ disk_stat_read(disk, write_sectors) -
+ disk->sync_io;
if ((curr_events - rdev->last_events) > 32) {
rdev->last_events = curr_events;
idle = 0;
diff -puN fs/partitions/check.c~per-cpu-disk-stats fs/partitions/check.c
--- 25/fs/partitions/check.c~per-cpu-disk-stats 2003-02-24 23:44:09.000000000 -0800
+++ 25-akpm/fs/partitions/check.c 2003-02-24 23:44:09.000000000 -0800
@@ -503,13 +503,7 @@ void del_gendisk(struct gendisk *disk)
disk->capacity = 0;
disk->flags &= ~GENHD_FL_UP;
unlink_gendisk(disk);
- disk->reads = disk->writes = 0;
- disk->read_sectors = disk->write_sectors = 0;
- disk->read_merges = disk->write_merges = 0;
- disk->read_ticks = disk->write_ticks = 0;
- disk->in_flight = 0;
- disk->io_ticks = 0;
- disk->time_in_queue = 0;
+ disk_stat_set_all(disk, 0);
disk->stamp = disk->stamp_idle = 0;
devfs_remove_partitions(disk);
if (disk->driverfs_dev) {
diff -puN include/linux/genhd.h~per-cpu-disk-stats include/linux/genhd.h
--- 25/include/linux/genhd.h~per-cpu-disk-stats 2003-02-24 23:44:09.000000000 -0800
+++ 25-akpm/include/linux/genhd.h 2003-02-24 23:46:31.000000000 -0800
@@ -70,6 +70,16 @@ struct hd_struct {
#define GENHD_FL_CD 8
#define GENHD_FL_UP 16

+struct disk_stats {
+ unsigned read_sectors, write_sectors;
+ unsigned reads, writes;
+ unsigned read_merges, write_merges;
+ unsigned read_ticks, write_ticks;
+ unsigned io_ticks;
+ int in_flight;
+ unsigned time_in_queue;
+};
+
struct gendisk {
int major; /* major number of driver */
int first_minor;
@@ -94,16 +104,86 @@ struct gendisk {
int policy;

unsigned sync_io; /* RAID */
- unsigned read_sectors, write_sectors;
- unsigned reads, writes;
- unsigned read_merges, write_merges;
- unsigned read_ticks, write_ticks;
- unsigned io_ticks;
- int in_flight;
unsigned long stamp, stamp_idle;
- unsigned time_in_queue;
+#ifdef CONFIG_SMP
+ struct disk_stats *dkstats;
+#else
+ struct disk_stats dkstats;
+#endif
};

+/*
+ * Macros to operate on percpu disk statistics:
+ * Since writes to disk_stats are serialised through the queue_lock,
+ * smp_processor_id() should be enough to get to the per_cpu versions
+ * of statistics counters
+ */
+#ifdef CONFIG_SMP
+#define disk_stat_add(gendiskp, field, addnd) \
+ (per_cpu_ptr(gendiskp->dkstats, smp_processor_id())->field += addnd)
+#define disk_stat_read(gendiskp, field) \
+({ \
+ typeof(gendiskp->dkstats->field) res = 0; \
+ int i; \
+ for (i=0; i < NR_CPUS; i++) { \
+ if (!cpu_possible(i)) \
+ continue; \
+ res += per_cpu_ptr(gendiskp->dkstats, i)->field; \
+ } \
+ res; \
+})
+
+static inline void disk_stat_set_all(struct gendisk *gendiskp, int value) {
+ int i;
+ for (i=0; i < NR_CPUS; i++) {
+ if (cpu_possible(i)) {
+ memset(per_cpu_ptr(gendiskp->dkstats, i), value,
+ sizeof (struct disk_stats));
+ }
+ }
+}
+
+#else
+#define disk_stat_add(gendiskp, field, addnd) (gendiskp->dkstats.field += addnd)
+#define disk_stat_read(gendiskp, field) (gendiskp->dkstats.field)
+
+static inline void disk_stat_set_all(struct gendisk *gendiskp, int value) {
+ memset(&gendiskp->dkstats, value, sizeof (struct disk_stats));
+}
+#endif
+
+#define disk_stat_inc(gendiskp, field) disk_stat_add(gendiskp, field, 1)
+#define disk_stat_dec(gendiskp, field) disk_stat_add(gendiskp, field, -1)
+#define disk_stat_sub(gendiskp, field, subnd) \
+ disk_stat_add(gendiskp, field, -subnd)
+
+
+/* Inlines to alloc and free disk stats in struct gendisk */
+#ifdef CONFIG_SMP
+static inline int init_disk_stats(struct gendisk *disk)
+{
+ disk->dkstats = kmalloc_percpu(sizeof (struct disk_stats), GFP_KERNEL);
+ if (!disk->dkstats)
+ return 0;
+ disk_stat_set_all(disk, 0);
+ return 1;
+}
+
+static inline void free_disk_stats(struct gendisk *disk)
+{
+ kfree_percpu(disk->dkstats);
+}
+#else /* CONFIG_SMP */
+static inline int init_disk_stats(struct gendisk *disk)
+{
+ return 1;
+}
+
+static inline void free_disk_stats(struct gendisk *disk)
+{
+}
+#endif /* CONFIG_SMP */
+
/* drivers/block/ll_rw_blk.c */
extern void disk_round_stats(struct gendisk *disk);

_

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