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block: Seperate read and write statistics of in_flight requests v2

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Commit a9327cac44 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 0f78ab9899

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>
This commit is contained in:
Nikanth Karthikesan
2009-10-06 20:16:55 +02:00
committed by Jens Axboe
parent 23e018a1b0
commit 316d315bff
6 changed files with 43 additions and 20 deletions
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21
include/linux/genhd.h
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@ -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);