Messages in this thread | | | From | Divyesh Shah <> | Date | Tue, 6 Apr 2010 10:00:07 -0700 | Subject | Re: [PATCH 2/3][v2] blkio: Add io controller stats like |
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On Tue, Apr 6, 2010 at 6:47 AM, Vivek Goyal <vgoyal@redhat.com> wrote: > On Mon, Apr 05, 2010 at 04:29:06PM -0700, Divyesh Shah wrote: >> On Mon, Apr 5, 2010 at 9:06 AM, Vivek Goyal <vgoyal@redhat.com> wrote: >> > On Fri, Apr 02, 2010 at 06:56:35PM -0700, Divyesh Shah wrote: >> >> - io_service_time (the actual time in ns taken by the dis to service the IO) >> >> - io_wait_time (the time spent waiting in the IO shceduler queues before >> >> getting serviced) >> >> - io_serviced (number of IOs serviced from this blkio_group) >> >> - io_service_bytes (Number of bytes served for this cgroup) >> >> >> >> These stats are accumulated per operation type helping us to distinguish between >> >> read and write, and sync and async IO. This patch does not increment any of >> >> these stats. >> >> >> >> Signed-off-by: Divyesh Shah<dpshah@google.com> >> >> --- >> >> >> >> Documentation/cgroups/blkio-controller.txt | 33 +++++ >> >> block/blk-cgroup.c | 179 +++++++++++++++++++++++++--- >> >> block/blk-cgroup.h | 41 +++++- >> >> block/cfq-iosched.c | 2 >> >> 4 files changed, 229 insertions(+), 26 deletions(-) >> >> >> >> diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt >> >> index 630879c..ededdca 100644 >> >> --- a/Documentation/cgroups/blkio-controller.txt >> >> +++ b/Documentation/cgroups/blkio-controller.txt >> >> @@ -75,6 +75,9 @@ CONFIG_DEBUG_BLK_CGROUP >> >> >> >> Details of cgroup files >> >> ======================= >> >> +Writing an int to any of the stats files (which excludes weight) will result >> >> +in all stats for that cgroup to be erased. >> >> + >> >> - blkio.weight >> >> - Specifies per cgroup weight. >> >> >> >> @@ -92,6 +95,36 @@ Details of cgroup files >> >> third field specifies the number of sectors transferred by the >> >> group to/from the device. >> >> >> >> +- blkio.io_service_bytes >> >> + - Number of bytes transferred to/from the disk by the group. These >> >> + are further divided by the type of operation - read or write, sync >> >> + or async. First two fields specify the major and minor number of the >> >> + device, third field specifies the operation type and the fourth field >> >> + specifies the number of bytes. >> >> + >> >> +- blkio.io_serviced >> >> + - Number of IOs completed to/from the disk by the group. These >> >> + are further divided by the type of operation - read or write, sync >> >> + or async. First two fields specify the major and minor number of the >> >> + device, third field specifies the operation type and the fourth field >> >> + specifies the number of IOs. >> >> + >> >> +- blkio.io_service_time >> >> + - Total amount of time spent by the device to service the IOs for this >> >> + cgroup. This is in nanoseconds to make it meaningful for flash >> >> + devices too. This time is further divided by the type of operation - >> >> + read or write, sync or async. First two fields specify the major and >> >> + minor number of the device, third field specifies the operation type >> >> + and the fourth field specifies the io_service_time in ns. >> > >> > Hi Divyesh, >> > >> > Looking the third patch where you acutally increment the stats, this is >> > how service time is calculated. >> > >> > - Save start_time in rq, when driver actually removes the request from >> > request queue. >> > - at request completion time calculate service time. >> > service_time = now - start_time. >> > >> > This works very well if driver/device does not have NCQ and process one >> > request at a time. But with NCQ, we can multiple requests in the driver >> > queue at the same time then we can run into issues. >> > >> > - With NCQ, time becomes cumulative. So if three requests rq1, rq2 and rq3 >> > are in disk queue, and if requests are processed in the order rq1,rq2,rq3 by >> > the disk (no parallel channles), then rq1 and rq2's completion time is >> > added in rq3. So total service time of the group can be much more than >> > actual time elapsed. That does not seem right. Did you face this issue in >> > your testing? >> >> You are right. With NCQ, the io_service_time numbers aren't exact. >> I've only tested this without NCQ for which these stats are accurate >> and very useful. With NCQ turned on I don't see a good way of getting >> this information accurately since only the disk knows when it actually >> starts to service a given request. With NCQ, io_service_time will have >> cumulative time as you pointed out which may still be useful for some >> high-level analysis if you also have the average queue depth for the >> device. >> > > Most of the modern disks now seem to be be NCQ. But I guess we can keep > those stats as it is useful for you on non NCQ setup. > >> io_wait_time stat makes sense with or w/o NCQ since its defined to >> only include the scheduler queueing time for each IO and is cumulative >> by design. I should probably reword the definition of io_service_time >> to indicate time after dispatch to the driver and request completion >> and also add a comment of how NCQ affects this stat. Sounds good? > > I am not sure if io_wait_time is cumulative by design. Think of this, > somebody says that this cgroup has waited for 1s on CFQ queue but actually > only .5 seconds have elapsed since the observation started. > > So I would say that please document it very properly in blkio-controller.txt > so that it is clear what exactly these numbers represent and what to expect on > NCQ disks.
Ok I will try to clarify further.
> > Thanks > Vivek > >> >> -Divyesh >> >> > >> > Same is the case with io_wait_time, Because time is cumulative, actual >> > io_wait_time, can be more than real time elapsed. >> > >> > Is this the intention and you are finding even cumulative time useful? >> > >> >> + >> >> +- blkio.io_wait_time >> >> + - Total amount of time the IO spent waiting in the scheduler queues for >> >> + service. This is in nanoseconds to make it meaningful for flash >> >> + devices too. This time is further divided by the type of operation - >> >> + read or write, sync or async. First two fields specify the major and >> >> + minor number of the device, third field specifies the operation type >> >> + and the fourth field specifies the io_wait_time in ns. >> >> + >> >> - blkio.dequeue >> >> - Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This >> >> gives the statistics about how many a times a group was dequeued >> >> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c >> >> index 5be3981..cac10b2 100644 >> >> --- a/block/blk-cgroup.c >> >> +++ b/block/blk-cgroup.c >> >> @@ -17,6 +17,8 @@ >> >> #include <linux/err.h> >> >> #include "blk-cgroup.h" >> >> >> >> +#define MAX_KEY_LEN 100 >> >> + >> >> static DEFINE_SPINLOCK(blkio_list_lock); >> >> static LIST_HEAD(blkio_list); >> >> >> >> @@ -55,12 +57,15 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup) >> >> } >> >> EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup); >> >> >> >> -void blkiocg_update_blkio_group_stats(struct blkio_group *blkg, >> >> - unsigned long time) >> >> +void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time) >> >> { >> >> - blkg->time += time; >> >> + unsigned long flags; >> >> + >> >> + spin_lock_irqsave(&blkg->stats_lock, flags); >> >> + blkg->stats.time += time; >> >> + spin_unlock_irqrestore(&blkg->stats_lock, flags); >> >> } >> >> -EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats); >> >> +EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used); >> >> >> >> void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg, >> >> struct blkio_group *blkg, void *key, dev_t dev) >> >> @@ -170,13 +175,119 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val) >> >> return 0; >> >> } >> >> >> >> -#define SHOW_FUNCTION_PER_GROUP(__VAR) \ >> >> +static int >> >> +blkiocg_reset_write(struct cgroup *cgroup, struct cftype *cftype, u64 val) >> >> +{ >> >> + struct blkio_cgroup *blkcg; >> >> + struct blkio_group *blkg; >> >> + struct hlist_node *n; >> >> + struct blkio_group_stats *stats; >> >> + >> >> + blkcg = cgroup_to_blkio_cgroup(cgroup); >> >> + spin_lock_irq(&blkcg->lock); >> >> + hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) { >> >> + spin_lock(&blkg->stats_lock); >> >> + stats = &blkg->stats; >> >> + memset(stats, 0, sizeof(struct blkio_group_stats)); >> >> + spin_unlock(&blkg->stats_lock); >> >> + } >> >> + spin_unlock_irq(&blkcg->lock); >> >> + return 0; >> >> +} >> >> + >> >> +static void blkio_get_key_name(int type, dev_t dev, char *str, int chars_left) >> >> +{ >> >> + snprintf(str, chars_left, "%u:%u", MAJOR(dev), MINOR(dev)); >> >> + chars_left -= strlen(str); >> >> + if (chars_left <= 0) { >> >> + printk(KERN_WARNING >> >> + "Possibly incorrect cgroup stat display format"); >> >> + return; >> >> + } >> >> + switch (type) { >> >> + case IO_READ: >> >> + strlcat(str, " Read", chars_left); >> >> + break; >> >> + case IO_WRITE: >> >> + strlcat(str, " Write", chars_left); >> >> + break; >> >> + case IO_SYNC: >> >> + strlcat(str, " Sync", chars_left); >> >> + break; >> >> + case IO_ASYNC: >> >> + strlcat(str, " Async", chars_left); >> >> + break; >> >> + case IO_TYPE_TOTAL: >> >> + strlcat(str, " Total", chars_left); >> >> + break; >> >> + default: >> >> + strlcat(str, " Invalid", chars_left); >> >> + } >> >> +} >> >> + >> >> +typedef uint64_t (get_var) (struct blkio_group *, int); >> >> + >> >> +static uint64_t blkio_get_typed_stat(struct blkio_group *blkg, >> >> + struct cgroup_map_cb *cb, get_var *getvar, dev_t dev) >> >> +{ >> >> + uint64_t disk_total; >> >> + char key_str[MAX_KEY_LEN]; >> >> + int type; >> >> + >> >> + for (type = 0; type < IO_TYPE_TOTAL; type++) { >> >> + blkio_get_key_name(type, dev, key_str, MAX_KEY_LEN); >> >> + cb->fill(cb, key_str, getvar(blkg, type)); >> >> + } >> >> + disk_total = getvar(blkg, IO_READ) + getvar(blkg, IO_WRITE); >> >> + blkio_get_key_name(IO_TYPE_TOTAL, dev, key_str, MAX_KEY_LEN); >> >> + cb->fill(cb, key_str, disk_total); >> >> + return disk_total; >> >> +} >> >> + >> >> +static uint64_t blkio_get_stat(struct blkio_group *blkg, >> >> + struct cgroup_map_cb *cb, get_var *getvar, dev_t dev) >> >> +{ >> >> + uint64_t var = getvar(blkg, 0); >> >> + char str[10]; >> >> + >> >> + snprintf(str, 10, "%u:%u", MAJOR(dev), MINOR(dev)); >> >> + cb->fill(cb, str, var); >> >> + return var; >> >> +} >> >> + >> >> +#define GET_STAT_INDEXED(__VAR) \ >> >> +uint64_t blkio_get_##__VAR##_stat(struct blkio_group *blkg, int type) \ >> >> +{ \ >> >> + return blkg->stats.__VAR[type]; \ >> >> +} \ >> >> + >> >> +GET_STAT_INDEXED(io_service_bytes); >> >> +GET_STAT_INDEXED(io_serviced); >> >> +GET_STAT_INDEXED(io_service_time); >> >> +GET_STAT_INDEXED(io_wait_time); >> >> +#undef GET_STAT_INDEXED >> >> + >> >> +#define GET_STAT(__VAR) \ >> >> +uint64_t blkio_get_##__VAR##_stat(struct blkio_group *blkg, int dummy) \ >> >> +{ \ >> >> + return blkg->stats.__VAR; \ >> >> +} >> >> + >> >> +GET_STAT(time); >> >> +GET_STAT(sectors); >> >> +#ifdef CONFIG_DEBUG_BLK_CGROUP >> >> +GET_STAT(dequeue); >> >> +#endif >> >> +#undef GET_STAT >> >> + >> >> +#define SHOW_FUNCTION_PER_GROUP(__VAR, get_stats, getvar, show_total) \ >> >> static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \ >> >> - struct cftype *cftype, struct seq_file *m) \ >> >> + struct cftype *cftype, struct cgroup_map_cb *cb) \ >> >> { \ >> >> struct blkio_cgroup *blkcg; \ >> >> struct blkio_group *blkg; \ >> >> struct hlist_node *n; \ >> >> + uint64_t cgroup_total = 0; \ >> >> \ >> >> if (!cgroup_lock_live_group(cgroup)) \ >> >> return -ENODEV; \ >> >> @@ -184,19 +295,32 @@ static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \ >> >> blkcg = cgroup_to_blkio_cgroup(cgroup); \ >> >> rcu_read_lock(); \ >> >> hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\ >> >> - if (blkg->dev) \ >> >> - seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev), \ >> >> - MINOR(blkg->dev), blkg->__VAR); \ >> >> + if (blkg->dev) { \ >> >> + spin_lock_irq(&blkg->stats_lock); \ >> >> + cgroup_total += get_stats(blkg, cb, getvar, \ >> >> + blkg->dev); \ >> >> + spin_unlock_irq(&blkg->stats_lock); \ >> >> + } \ >> >> } \ >> >> + if (show_total) \ >> >> + cb->fill(cb, "Total", cgroup_total); \ >> >> rcu_read_unlock(); \ >> >> cgroup_unlock(); \ >> >> return 0; \ >> >> } >> >> >> >> -SHOW_FUNCTION_PER_GROUP(time); >> >> -SHOW_FUNCTION_PER_GROUP(sectors); >> >> +SHOW_FUNCTION_PER_GROUP(time, blkio_get_stat, blkio_get_time_stat, 0); >> >> +SHOW_FUNCTION_PER_GROUP(sectors, blkio_get_stat, blkio_get_sectors_stat, 0); >> >> +SHOW_FUNCTION_PER_GROUP(io_service_bytes, blkio_get_typed_stat, >> >> + blkio_get_io_service_bytes_stat, 1); >> >> +SHOW_FUNCTION_PER_GROUP(io_serviced, blkio_get_typed_stat, >> >> + blkio_get_io_serviced_stat, 1); >> >> +SHOW_FUNCTION_PER_GROUP(io_service_time, blkio_get_typed_stat, >> >> + blkio_get_io_service_time_stat, 1); >> >> +SHOW_FUNCTION_PER_GROUP(io_wait_time, blkio_get_typed_stat, >> >> + blkio_get_io_wait_time_stat, 1); >> >> #ifdef CONFIG_DEBUG_BLK_CGROUP >> >> -SHOW_FUNCTION_PER_GROUP(dequeue); >> >> +SHOW_FUNCTION_PER_GROUP(dequeue, blkio_get_stat, blkio_get_dequeue_stat, 0); >> >> #endif >> >> #undef SHOW_FUNCTION_PER_GROUP >> >> >> >> @@ -204,7 +328,7 @@ SHOW_FUNCTION_PER_GROUP(dequeue); >> >> void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg, >> >> unsigned long dequeue) >> >> { >> >> - blkg->dequeue += dequeue; >> >> + blkg->stats.dequeue += dequeue; >> >> } >> >> EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats); >> >> #endif >> >> @@ -217,16 +341,39 @@ struct cftype blkio_files[] = { >> >> }, >> >> { >> >> .name = "time", >> >> - .read_seq_string = blkiocg_time_read, >> >> + .read_map = blkiocg_time_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> }, >> >> { >> >> .name = "sectors", >> >> - .read_seq_string = blkiocg_sectors_read, >> >> + .read_map = blkiocg_sectors_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> + }, >> >> + { >> >> + .name = "io_service_bytes", >> >> + .read_map = blkiocg_io_service_bytes_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> + }, >> >> + { >> >> + .name = "io_serviced", >> >> + .read_map = blkiocg_io_serviced_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> + }, >> >> + { >> >> + .name = "io_service_time", >> >> + .read_map = blkiocg_io_service_time_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> + }, >> >> + { >> >> + .name = "io_wait_time", >> >> + .read_map = blkiocg_io_wait_time_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> }, >> >> #ifdef CONFIG_DEBUG_BLK_CGROUP >> >> { >> >> .name = "dequeue", >> >> - .read_seq_string = blkiocg_dequeue_read, >> >> + .read_map = blkiocg_dequeue_read, >> >> + .write_u64 = blkiocg_reset_write, >> >> }, >> >> #endif >> >> }; >> >> diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h >> >> index fe44517..e8600b0 100644 >> >> --- a/block/blk-cgroup.h >> >> +++ b/block/blk-cgroup.h >> >> @@ -23,6 +23,14 @@ extern struct cgroup_subsys blkio_subsys; >> >> #define blkio_subsys_id blkio_subsys.subsys_id >> >> #endif >> >> >> >> +enum io_type { >> >> + IO_READ = 0, >> >> + IO_WRITE, >> >> + IO_SYNC, >> >> + IO_ASYNC, >> >> + IO_TYPE_TOTAL >> >> +}; >> >> + >> >> struct blkio_cgroup { >> >> struct cgroup_subsys_state css; >> >> unsigned int weight; >> >> @@ -30,6 +38,23 @@ struct blkio_cgroup { >> >> struct hlist_head blkg_list; >> >> }; >> >> >> >> +struct blkio_group_stats { >> >> + /* total disk time and nr sectors dispatched by this group */ >> >> + uint64_t time; >> >> + uint64_t sectors; >> >> + /* Total disk time used by IOs in ns */ >> >> + uint64_t io_service_time[IO_TYPE_TOTAL]; >> >> + uint64_t io_service_bytes[IO_TYPE_TOTAL]; /* Total bytes transferred */ >> >> + /* Total IOs serviced, post merge */ >> >> + uint64_t io_serviced[IO_TYPE_TOTAL]; >> >> + /* Total time spent waiting in scheduler queue in ns */ >> >> + uint64_t io_wait_time[IO_TYPE_TOTAL]; >> >> +#ifdef CONFIG_DEBUG_BLK_CGROUP >> >> + /* How many times this group has been removed from service tree */ >> >> + unsigned long dequeue; >> >> +#endif >> >> +}; >> >> + >> >> struct blkio_group { >> >> /* An rcu protected unique identifier for the group */ >> >> void *key; >> >> @@ -38,15 +63,13 @@ struct blkio_group { >> >> #ifdef CONFIG_DEBUG_BLK_CGROUP >> >> /* Store cgroup path */ >> >> char path[128]; >> >> - /* How many times this group has been removed from service tree */ >> >> - unsigned long dequeue; >> >> #endif >> >> /* The device MKDEV(major, minor), this group has been created for */ >> >> - dev_t dev; >> >> + dev_t dev; >> >> >> >> - /* total disk time and nr sectors dispatched by this group */ >> >> - unsigned long time; >> >> - unsigned long sectors; >> >> + /* Need to serialize the stats in the case of reset/update */ >> >> + spinlock_t stats_lock; >> >> + struct blkio_group_stats stats; >> >> }; >> >> >> >> typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg); >> >> @@ -105,8 +128,8 @@ extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg, >> >> extern int blkiocg_del_blkio_group(struct blkio_group *blkg); >> >> extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, >> >> void *key); >> >> -void blkiocg_update_blkio_group_stats(struct blkio_group *blkg, >> >> - unsigned long time); >> >> +void blkiocg_update_timeslice_used(struct blkio_group *blkg, >> >> + unsigned long time); >> >> #else >> >> struct cgroup; >> >> static inline struct blkio_cgroup * >> >> @@ -122,7 +145,7 @@ blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; } >> >> >> >> static inline struct blkio_group * >> >> blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; } >> >> -static inline void blkiocg_update_blkio_group_stats(struct blkio_group *blkg, >> >> +static inline void blkiocg_update_timeslice_used(struct blkio_group *blkg, >> >> unsigned long time) {} >> >> #endif >> >> #endif /* _BLK_CGROUP_H */ >> >> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c >> >> index c18e348..d91df9f 100644 >> >> --- a/block/cfq-iosched.c >> >> +++ b/block/cfq-iosched.c >> >> @@ -914,7 +914,7 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg, >> >> >> >> cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime, >> >> st->min_vdisktime); >> >> - blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl); >> >> + blkiocg_update_timeslice_used(&cfqg->blkg, used_sl); >> >> } >> >> >> >> #ifdef CONFIG_CFQ_GROUP_IOSCHED >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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