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Message-ID: <h2vaf41c7c41004021353k37e6b085ma0e7acebdf37c65b@mail.gmail.com>
Date: Fri, 2 Apr 2010 13:53:30 -0700
From: Divyesh Shah <dpshah@...gle.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: jens.axboe@...cle.com, linux-kernel@...r.kernel.org,
nauman@...gle.com, ctalbott@...gle.com
Subject: Re: [PATCH 2/3] blkio: Add io controller stats like
Vivek, thanks for the detailed review. Comments inline. I'll send a V2
patchset soon.
On Fri, Apr 2, 2010 at 11:10 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> On Thu, Apr 01, 2010 at 03:01:24PM -0700, Divyesh Shah wrote:
>> - io_service_time
>> - io_wait_time
>> - io_serviced
>> - io_service_bytes
>>
>
> Hi Divyesh,
>
> Some more description what exactly these stats are will be helpful. Please
> also update Documentation/cgroup/blkio-controller.txt file appropriately.
> Especially, "Details of cgroup files" section.
Done. Will be in V2
>
>> 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@...gle.com>
>> ---
>>
>> block/blk-cgroup.c | 178 ++++++++++++++++++++++++++++++++++++++++++++++-----
>> block/blk-cgroup.h | 39 +++++++++--
>> block/cfq-iosched.c | 2 -
>> 3 files changed, 194 insertions(+), 25 deletions(-)
>>
>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
>> index 5be3981..ad6843f 100644
>> --- a/block/blk-cgroup.c
>> +++ b/block/blk-cgroup.c
>> @@ -55,12 +55,15 @@ 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 +173,121 @@ 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;
>> +}
>> +
>> +void get_key_name(int type, char *disk_id, char *str, int chars_left)
>> +{
>
> get_key_name() should be static? Can we prefix all these internal function
> names with blkio?
Done. Will be in V2.
>
> Do we have to introduce this separate notion of char *disk_id. Can we
> simply stick to dev_t and do the sprintf like functions to convert that
> into key. For me personally it is just less confusion while reading code.
>
>> + strlcpy(str, disk_id, chars_left);
>> + 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_MAX:
>> + strlcat(str, " Total", chars_left);
>> + break;
>
> Should we use IO_TYPE_TOTAL for "Total" stats.
Can certainly replace MAX with TOTAL.
>
>> + default:
>> + strlcat(str, " Invalid", chars_left);
>> + }
>> +}
>> +
>> +typedef uint64_t (get_var) (struct blkio_group *, int);
>> +
>> +#define MAX_KEY_LEN 100
>
> Can we move above define to the beginning of the file. So that it is
> easily visible.
Done
>
>> +uint64_t get_typed_stat(struct blkio_group *blkg, struct cgroup_map_cb *cb,
>> + get_var *getvar, char *disk_id)
>> +{
>
> static function? blkio_get_typed_stat()?
Done
>
> Again, can we use dev_t instead of char *disk_id.
Good point. Done
>
>> + uint64_t disk_total;
>> + char key_str[MAX_KEY_LEN];
>> + int type;
>> +
>> + for (type = 0; type < IO_TYPE_MAX; type++) {
>> + get_key_name(type, disk_id, key_str, MAX_KEY_LEN);
>> + cb->fill(cb, key_str, getvar(blkg, type));
>> + }
>> + disk_total = getvar(blkg, IO_READ) + getvar(blkg, IO_WRITE);
>> + get_key_name(IO_TYPE_MAX, disk_id, key_str, MAX_KEY_LEN);
>> + cb->fill(cb, key_str, disk_total);
>> + return disk_total;
>> +}
>> +
>> +uint64_t get_stat(struct blkio_group *blkg, struct cgroup_map_cb *cb,
>> + get_var *getvar, char *disk_id)
>> +{
>> + uint64_t var = getvar(blkg, 0);
>> + cb->fill(cb, disk_id, var);
>> + return var;
>> +}
>> +
>> +#define GET_STAT_INDEXED(__VAR) \
>> +uint64_t 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, __CONV) \
>> +uint64_t get_##__VAR##_stat(struct blkio_group *blkg, int dummy) \
>> +{ \
>> + uint64_t data = blkg->stats.__VAR; \
>> + if (__CONV) \
>> + data = (uint64_t)jiffies_to_msecs(data) * NSEC_PER_MSEC;\
>> + return data; \
>> +}
>> +
>> +GET_STAT(time, 1);
>> +GET_STAT(sectors, 0);
>> +#ifdef CONFIG_DEBUG_BLK_CGROUP
>> +GET_STAT(dequeue, 0);
>> +#endif
>> +#undef GET_STAT
>> +
>
> I think now so many macros to define different kind of functions is
> becoming really confusing. How about creating a two dimensional stat
> array which is indexed by type of io stat like "io_service_time" and
> then indexed by sub io type that is "READ, WRITE, SYNC" etc. And we
> can define a single function to read all kind of stats.
>
> That way we will not have to define one GET_STAT_INDEXED() and GET_STAT()
> for each unindexed variable. If there are not multiple functions then,
> then everywhere we don't have to pass around a function pointer to read
> the variable stat and code should become much simpler. Example, code
> follows.
>
>
> enum stat_type {
> BLKIO_STAT_TIME
> BLKIO_STAT_SECTORS
> BLKIO_STAT_WAIT_TIME
> BLKIO_STAT_SERVICE_TIME
> }
>
> enum stat_sub_type {
> BLKIO_STAT_READ
> BLKIO_STAT_WRITE
> BLKIO_STAT_SYNC
> }
>
> blkio_get_stat_var(enum stat_type var, enum stat_sub_type var_type) {
>
> if (var == BLKIO_STAT_TIME)
> reutrn blkg->stat.time
>
> /* Same as above for sectors */
>
> return blkg->stat[var][var_type];
> }
I'm not sure adding this level of complexity (2nd dimension for stats)
and the numerous if (..) statements (or switch) is warranted when they
only apply for the get_stat() and get_typed_stat() functions. This
seems like a more complicated simplification :).
>
> Also all these get_* function needs to be static.
Done
>
>> +#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; \
>> + char disk_id[10]; \
>> \
>> 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); \
>> + snprintf(disk_id, 10, "%u:%u", MAJOR(blkg->dev),\
>> + MINOR(blkg->dev)); \
>> + cgroup_total += get_stats(blkg, cb, getvar, \
>> + disk_id); \
>> + 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, get_stat, get_time_stat, 0);
>> +SHOW_FUNCTION_PER_GROUP(sectors, get_stat, get_sectors_stat, 0);
>> +SHOW_FUNCTION_PER_GROUP(io_service_bytes, get_typed_stat,
>> + get_io_service_bytes_stat, 1);
>> +SHOW_FUNCTION_PER_GROUP(io_serviced, get_typed_stat, get_io_serviced_stat, 1);
>> +SHOW_FUNCTION_PER_GROUP(io_service_time, get_typed_stat,
>> + get_io_service_time_stat, 1);
>> +SHOW_FUNCTION_PER_GROUP(io_wait_time, get_typed_stat, get_io_wait_time_stat, 1);
>> #ifdef CONFIG_DEBUG_BLK_CGROUP
>> -SHOW_FUNCTION_PER_GROUP(dequeue);
>> +SHOW_FUNCTION_PER_GROUP(dequeue, get_stat, 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 +341,38 @@ 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,
>> },
>
> blkiocg_reset_write() is invoked if a user does some write on any of the
> above files. This will reset all the stats. So if I do echo x >
> blkio.time, I will see all other files being reset? I think this is
> little counter intutive.
>
> Either we need to reset only those specific stats (the file being written
> to) or may be we can provide a separate file "blkio.reset_stats" to reset
> all the stats?
I added a note in the Documentation file that writing an int to any of
the stats should reset all. I don't get the point of introducing
another file for this and would want stats to be cleared all together
in order to have say io_service_time and io_serviced in sync, i.e.,
the io_service_time should always be the total service time for the
IOs accounted for in io_serviced.
> Secondly, instead of providing separate files for all the stats
> "io_service_bytes, io_serviced...." do you think it makes sense to put
> these in a single file "blkio.stat". Something like what memory controller
> does for providing stats in a single file. I think number of files per
> cgroup will be little less overwhelming that way.
>
> Thinking loud, Hm.., but these stats are per device (unlink memory cgroup)
> that too each stat has been broken down by type (READ, WRITE, SYNC..etc), so it
> might be too much of info in a single file. That way, keeping these in
> separate files makese sense. I guess, per stat file is ok, given the
> fact that stats are per device.
Yeah we'd rather keep them separate.
>
> Thanks
> Vivek
>
>> #ifdef CONFIG_DEBUG_BLK_CGROUP
>> {
>> .name = "dequeue",
>> - .read_seq_string = blkiocg_dequeue_read,
>> + .read_map = blkiocg_dequeue_read,
>> },
>> #endif
>> };
>> diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
>> index fe44517..5c5e529 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_MAX
>> +};
>> +
>> 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_MAX];
>> + uint64_t io_service_bytes[IO_TYPE_MAX]; /* Total bytes transferred */
>> + /* Total IOs serviced, post merge */
>> + uint64_t io_serviced[IO_TYPE_MAX];
>> + /* Total time spent waiting in scheduler queue in ns */
>> + uint64_t io_wait_time[IO_TYPE_MAX];
>> +#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;
>>
>> - /* 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
>
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