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Message-ID: <s2haf41c7c41004060959j8d49feccx385545e66288c185@mail.gmail.com>
Date: Tue, 6 Apr 2010 09:59:32 -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][v3] blkio: Add io controller stats like
Vivek,
I'll send out a v3.1 only for this patch since you've Acked the
other 2 patches. Thanks a lot for the detailed reviews again!
On Tue, Apr 6, 2010 at 8:16 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> On Mon, Apr 05, 2010 at 08:37:01PM -0700, Divyesh Shah wrote:
>> - io_service_time (the time between request dispatch and completion for IOs
>> in the cgroup)
>> - 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@...gle.com>
>> ---
>>
>> Documentation/cgroups/blkio-controller.txt | 40 +++++++
>> block/blk-cgroup.c | 166 +++++++++++++++++++++++++---
>> block/blk-cgroup.h | 60 ++++++++--
>> block/cfq-iosched.c | 3 -
>> 4 files changed, 239 insertions(+), 30 deletions(-)
>>
>> diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
>> index 630879c..087925b 100644
>> --- a/Documentation/cgroups/blkio-controller.txt
>> +++ b/Documentation/cgroups/blkio-controller.txt
>> @@ -77,7 +77,6 @@ Details of cgroup files
>> =======================
>> - blkio.weight
>> - Specifies per cgroup weight.
>> -
>> Currently allowed range of weights is from 100 to 1000.
>>
>> - blkio.time
>> @@ -92,6 +91,41 @@ 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.
>> +
>
> Hi Divyesh,
>
> V3 looks much better. Just couple of minor nits.
>
>> +- blkio.io_service_time
>> + - Total amount of time between request dispatch and request completion
>> + for the IOs done by this cgroup. This is in nanoseconds to make it
>> + meaningful for flash devices too. For devices with queue depth of 1,
>> + this time represents the actual service time. When queue_depth > 1,
>> + that is no longer true as requests may be served out of order.
>
> Like io_wait_time, can you also mention here that this time is cumulative
> time and on NCQ disks it can be more than actual time elapsed.
Will do.
>
> I did a quick run with your patches. I ran a sequential workload for 30s
> in two groups of weight 100 and 200. Following is the output of
> blkio.io_service_time (I have kept stats for only disk 253:3 in output).
>
> # cat test1/blkio.io_service_time
> 253:3 Read 18019970625
> 253:3 Write 0
> 253:3 Sync 18019970625
> 253:3 Async 0
> 253:3 Total 18019970625
>
> # cat test2/blkio.io_service_time
> 253:3 Read 35479070171
> 253:3 Write 0
> 253:3 Sync 35479070171
> 253:3 Async 0
>
> This storage supports NCQ. We see that though I ran test only for
> 30 seconds, total service ime for cgroup is close to 18+35=53 seconds.
Yes that is expected as from our discussion about NCQ as any IO can
have the service time of multiple IOs coupled together when serviced
out of order.
>
>> + 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.
>> +
>> +- blkio.io_wait_time
>> + - Total amount of time the IO spent waiting in the scheduler queues for
>> + service. This can be greater than the total time elapsed since it is
>> + cumulative io_wait_time for all IOs. 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
>> @@ -99,6 +133,10 @@ Details of cgroup files
>> and minor number of the device and third field specifies the number
>> of times a group was dequeued from a particular device.
>>
>> +- blkio.reset_stats
>> + - Writing an int to this file will result in resetting all the stats
>> + for that cgroup.
>> +
>
> Personally, I like adding a separate file to reset the stats. Now one does
> not get surprised by the fact that writting to blkio.io_service_time, also
> reset rest of the stats.
>
>> CFQ sysfs tunable
>> =================
>> /sys/block/<disk>/queue/iosched/group_isolation
>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
>> index 5be3981..d585a05 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 +57,21 @@ 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 blkio_group_init(struct blkio_group *blkg)
>> +{
>> + spin_lock_init(&blkg->stats_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(blkio_group_init);
>> +
>> +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 +181,107 @@ 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)
>> +{
>
> I guess we can rename this function to blkiocg_reset_stats().
Will do
>
> [..]
>> @@ -217,16 +331,36 @@ struct cftype blkio_files[] = {
>> },
>> {
>> .name = "time",
>> - .read_seq_string = blkiocg_time_read,
>> + .read_map = blkiocg_time_read,
>> },
>> {
>> .name = "sectors",
>> - .read_seq_string = blkiocg_sectors_read,
>> + .read_map = blkiocg_sectors_read,
>> + },
>> + {
>> + .name = "io_service_bytes",
>> + .read_map = blkiocg_io_service_bytes_read,
>> + },
>> + {
>> + .name = "io_serviced",
>> + .read_map = blkiocg_io_serviced_read,
>> + },
>> + {
>> + .name = "io_service_time",
>> + .read_map = blkiocg_io_service_time_read,
>> + },
>> + {
>> + .name = "io_wait_time",
>> + .read_map = blkiocg_io_wait_time_read,
>> + },
>> + {
>> + .name = "reset_stats",
>> + .write_u64 = blkiocg_reset_write,
>
> use blkiocg_reset_stats?
Will do
>
> Thanks
> Vivek
>
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