From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756921Ab0DEX3f (ORCPT ); Mon, 5 Apr 2010 19:29:35 -0400 Received: from smtp-out.google.com ([216.239.44.51]:11915 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756727Ab0DEX33 convert rfc822-to-8bit (ORCPT ); Mon, 5 Apr 2010 19:29:29 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:from:date:message-id: subject:to:cc:content-type:content-transfer-encoding:x-system-of-record; b=G84NZkR8s7a1LAbLyixdJDoEuvPwIRSrZAgIb9EKLUMdOozztL7Z+qYtUDnszuZh1 7RcWbpBbao5pmO0GHAJJw== MIME-Version: 1.0 In-Reply-To: <20100405160606.GF876@redhat.com> References: <20100403014724.30746.16081.stgit@austin.mtv.corp.google.com> <20100403015553.30746.86746.stgit@austin.mtv.corp.google.com> <20100405160606.GF876@redhat.com> From: Divyesh Shah Date: Mon, 5 Apr 2010 16:29:06 -0700 Message-ID: Subject: Re: [PATCH 2/3][v2] blkio: Add io controller stats like To: Vivek Goyal Cc: jens.axboe@oracle.com, linux-kernel@vger.kernel.org, nauman@google.com, ctalbott@google.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 5, 2010 at 9:06 AM, Vivek Goyal 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 >> --- >> >>  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. 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? -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 >>  #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 >