block: Seperate read and write statistics of in_flight requests v2
Nikanth Karthikesan [Tue, 6 Oct 2009 18:16:55 +0000 (20:16 +0200)]
Commit a9327cac440be4d8333bba975cbbf76045096275 added seperate read
and write statistics of in_flight requests. And exported the number
of read and write requests in progress seperately through sysfs.

But  Corrado Zoccolo <czoccolo@gmail.com> reported getting strange
output from "iostat -kx 2". Global values for service time and
utilization were garbage. For interval values, utilization was always
100%, and service time is higher than normal.

So this was reverted by commit 0f78ab9899e9d6acb09d5465def618704255963b

The problem was in part_round_stats_single(), I missed the following:
        if (now == part->stamp)
                return;

-       if (part->in_flight) {
+       if (part_in_flight(part)) {
                __part_stat_add(cpu, part, time_in_queue,
                                part_in_flight(part) * (now - part->stamp));
                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));

With this chunk included, the reported regression gets fixed.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>

--
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blk-core.c
block/blk-merge.c
block/genhd.c
drivers/md/dm.c
fs/partitions/check.c
include/linux/genhd.h

index 73ecbed..ac0fa10 100644 (file)
@@ -70,7 +70,7 @@ static void drive_stat_acct(struct request *rq, int new_io)
                part_stat_inc(cpu, part, merges[rw]);
        else {
                part_round_stats(cpu, part);
-               part_inc_in_flight(part);
+               part_inc_in_flight(part, rw);
        }
 
        part_stat_unlock();
@@ -1030,9 +1030,9 @@ static void part_round_stats_single(int cpu, struct hd_struct *part,
        if (now == part->stamp)
                return;
 
-       if (part->in_flight) {
+       if (part_in_flight(part)) {
                __part_stat_add(cpu, part, time_in_queue,
-                               part->in_flight * (now - part->stamp));
+                               part_in_flight(part) * (now - part->stamp));
                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
        }
        part->stamp = now;
@@ -1739,7 +1739,7 @@ static void blk_account_io_done(struct request *req)
                part_stat_inc(cpu, part, ios[rw]);
                part_stat_add(cpu, part, ticks[rw], duration);
                part_round_stats(cpu, part);
-               part_dec_in_flight(part);
+               part_dec_in_flight(part, rw);
 
                part_stat_unlock();
        }
index b0de857..99cb5cf 100644 (file)
@@ -351,7 +351,7 @@ static void blk_account_io_merge(struct request *req)
                part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
 
                part_round_stats(cpu, part);
-               part_dec_in_flight(part);
+               part_dec_in_flight(part, rq_data_dir(req));
 
                part_stat_unlock();
        }
index 5a0861d..517e433 100644 (file)
@@ -869,6 +869,7 @@ static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);
 static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
+static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 static struct device_attribute dev_attr_fail =
        __ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);
@@ -888,6 +889,7 @@ static struct attribute *disk_attrs[] = {
        &dev_attr_alignment_offset.attr,
        &dev_attr_capability.attr,
        &dev_attr_stat.attr,
+       &dev_attr_inflight.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
        &dev_attr_fail.attr,
 #endif
@@ -1053,7 +1055,7 @@ static int diskstats_show(struct seq_file *seqf, void *v)
                           part_stat_read(hd, merges[1]),
                           (unsigned long long)part_stat_read(hd, sectors[1]),
                           jiffies_to_msecs(part_stat_read(hd, ticks[1])),
-                          hd->in_flight,
+                          part_in_flight(hd),
                           jiffies_to_msecs(part_stat_read(hd, io_ticks)),
                           jiffies_to_msecs(part_stat_read(hd, time_in_queue))
                        );
index 23e76fe..376f1ab 100644 (file)
@@ -130,7 +130,7 @@ struct mapped_device {
        /*
         * A list of ios that arrived while we were suspended.
         */
-       atomic_t pending;
+       atomic_t pending[2];
        wait_queue_head_t wait;
        struct work_struct work;
        struct bio_list deferred;
@@ -453,13 +453,14 @@ static void start_io_acct(struct dm_io *io)
 {
        struct mapped_device *md = io->md;
        int cpu;
+       int rw = bio_data_dir(io->bio);
 
        io->start_time = jiffies;
 
        cpu = part_stat_lock();
        part_round_stats(cpu, &dm_disk(md)->part0);
        part_stat_unlock();
-       dm_disk(md)->part0.in_flight = atomic_inc_return(&md->pending);
+       dm_disk(md)->part0.in_flight[rw] = atomic_inc_return(&md->pending[rw]);
 }
 
 static void end_io_acct(struct dm_io *io)
@@ -479,8 +480,9 @@ static void end_io_acct(struct dm_io *io)
         * After this is decremented the bio must not be touched if it is
         * a barrier.
         */
-       dm_disk(md)->part0.in_flight = pending =
-               atomic_dec_return(&md->pending);
+       dm_disk(md)->part0.in_flight[rw] = pending =
+               atomic_dec_return(&md->pending[rw]);
+       pending += atomic_read(&md->pending[rw^0x1]);
 
        /* nudge anyone waiting on suspend queue */
        if (!pending)
@@ -1785,7 +1787,8 @@ static struct mapped_device *alloc_dev(int minor)
        if (!md->disk)
                goto bad_disk;
 
-       atomic_set(&md->pending, 0);
+       atomic_set(&md->pending[0], 0);
+       atomic_set(&md->pending[1], 0);
        init_waitqueue_head(&md->wait);
        INIT_WORK(&md->work, dm_wq_work);
        init_waitqueue_head(&md->eventq);
@@ -2088,7 +2091,8 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
                                break;
                        }
                        spin_unlock_irqrestore(q->queue_lock, flags);
-               } else if (!atomic_read(&md->pending))
+               } else if (!atomic_read(&md->pending[0]) &&
+                                       !atomic_read(&md->pending[1]))
                        break;
 
                if (interruptible == TASK_INTERRUPTIBLE &&
index f38fee0..7b685e1 100644 (file)
@@ -248,11 +248,19 @@ ssize_t part_stat_show(struct device *dev,
                part_stat_read(p, merges[WRITE]),
                (unsigned long long)part_stat_read(p, sectors[WRITE]),
                jiffies_to_msecs(part_stat_read(p, ticks[WRITE])),
-               p->in_flight,
+               part_in_flight(p),
                jiffies_to_msecs(part_stat_read(p, io_ticks)),
                jiffies_to_msecs(part_stat_read(p, time_in_queue)));
 }
 
+ssize_t part_inflight_show(struct device *dev,
+                       struct device_attribute *attr, char *buf)
+{
+       struct hd_struct *p = dev_to_part(dev);
+
+       return sprintf(buf, "%8u %8u\n", p->in_flight[0], p->in_flight[1]);
+}
+
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 ssize_t part_fail_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
@@ -281,6 +289,7 @@ static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
 static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, part_alignment_offset_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
+static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 static struct device_attribute dev_attr_fail =
        __ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);
@@ -292,6 +301,7 @@ static struct attribute *part_attrs[] = {
        &dev_attr_size.attr,
        &dev_attr_alignment_offset.attr,
        &dev_attr_stat.attr,
+       &dev_attr_inflight.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
        &dev_attr_fail.attr,
 #endif
index 7beaa21..297df45 100644 (file)
@@ -98,7 +98,7 @@ struct hd_struct {
        int make_it_fail;
 #endif
        unsigned long stamp;
-       int in_flight;
+       int in_flight[2];
 #ifdef CONFIG_SMP
        struct disk_stats *dkstats;
 #else
@@ -322,18 +322,23 @@ static inline void free_part_stats(struct hd_struct *part)
 #define part_stat_sub(cpu, gendiskp, field, subnd)                     \
        part_stat_add(cpu, gendiskp, field, -subnd)
 
-static inline void part_inc_in_flight(struct hd_struct *part)
+static inline void part_inc_in_flight(struct hd_struct *part, int rw)
 {
-       part->in_flight++;
+       part->in_flight[rw]++;
        if (part->partno)
-               part_to_disk(part)->part0.in_flight++;
+               part_to_disk(part)->part0.in_flight[rw]++;
 }
 
-static inline void part_dec_in_flight(struct hd_struct *part)
+static inline void part_dec_in_flight(struct hd_struct *part, int rw)
 {
-       part->in_flight--;
+       part->in_flight[rw]--;
        if (part->partno)
-               part_to_disk(part)->part0.in_flight--;
+               part_to_disk(part)->part0.in_flight[rw]--;
+}
+
+static inline int part_in_flight(struct hd_struct *part)
+{
+       return part->in_flight[0] + part->in_flight[1];
 }
 
 /* block/blk-core.c */
@@ -546,6 +551,8 @@ extern ssize_t part_size_show(struct device *dev,
                              struct device_attribute *attr, char *buf);
 extern ssize_t part_stat_show(struct device *dev,
                              struct device_attribute *attr, char *buf);
+extern ssize_t part_inflight_show(struct device *dev,
+                             struct device_attribute *attr, char *buf);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 extern ssize_t part_fail_show(struct device *dev,
                              struct device_attribute *attr, char *buf);