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Date: Tue, 09 Mar 2010 09:52:06 +0800
From: Gui Jianfeng <guijianfeng@...fujitsu.com>
To: Vivek Goyal <vgoyal@...hat.com>,
Nauman Rafique <nauman@...gle.com>, jens.axboe@...cle.com
CC: Chad Talbott <ctalbott@...gle.com>, linux-kernel@...r.kernel.org,
Li Zefan <lizf@...fujitsu.com>
Subject: Re: [PATCH 1/2 V3] io-controller: Add a new interface "weight_device"
for IO-Controller
Vivek Goyal wrote:
> On Mon, Mar 08, 2010 at 11:39:54AM -0800, Nauman Rafique wrote:
>> On Fri, Mar 5, 2010 at 6:13 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
>>> On Fri, Mar 05, 2010 at 10:25:58AM +0800, Gui Jianfeng wrote:
>>>> Currently, IO Controller makes use of blkio.weight to assign weight for
>>>> all devices. Here a new user interface "blkio.weight_device" is introduced to
>>>> assign different weights for different devices. blkio.weight becomes the
>>>> default value for devices which are not configured by "blkio.weight_device"
>>>>
>>>> You can use the following format to assigned specific weight for a given
>>>> device:
>>>>
>>>> major:minor represents device number.
>>>>
>>>> And you can remove a specific weight as following:
>>>>
>>>> V1->V2 changes:
>>>> - use user interface "weight_device" instead of "policy" suggested by Vivek
>>>> - rename some struct suggested by Vivek
>>>> - rebase to 2.6-block "for-linus" branch
>>>> - remove an useless list_empty check pointed out by Li Zefan
>>>> - some trivial typo fix
>>>>
>>>> V2->V3 changes:
>>>> - Move policy_*_node() functions up to get rid of forward declarations
>>>> - rename related functions by adding prefix "blkio_"
>>>>
>>> Thanks for the changes Gui. Looks good to me.
>>>
>>> Acked-by: Vivek Goyal <vgoyal@...hat.com>
>>>
>>> Vivek
>>>
>>>> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
>>>> ---
>>>> block/blk-cgroup.c | 236 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>>>> block/blk-cgroup.h | 10 ++
>>>> block/cfq-iosched.c | 2 +-
>>>> 3 files changed, 246 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
>>>> index c85d74c..8825e49 100644
>>>> --- a/block/blk-cgroup.c
>>>> +++ b/block/blk-cgroup.c
>>>> @@ -16,6 +16,7 @@
>>>> #include <linux/module.h>
>>>> #include <linux/err.h>
>>>> #include "blk-cgroup.h"
>>>> +#include <linux/genhd.h>
>>>>
>>>> static DEFINE_SPINLOCK(blkio_list_lock);
>>>> static LIST_HEAD(blkio_list);
>>>> @@ -23,6 +24,32 @@ static LIST_HEAD(blkio_list);
>>>> struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
>>>> EXPORT_SYMBOL_GPL(blkio_root_cgroup);
>>>>
>>>> +static inline void blkio_policy_insert_node(struct blkio_cgroup *blkcg,
>>>> + struct blkio_policy_node *pn)
>>>> +{
>>>> + list_add(&pn->node, &blkcg->policy_list);
>>>> +}
>>>> +
>>>> +/* Must be called with blkcg->lock held */
>>>> +static inline void blkio_policy_delete_node(struct blkio_policy_node *pn)
>>>> +{
>>>> + list_del(&pn->node);
>>>> +}
>>>> +
>>>> +/* Must be called with blkcg->lock held */
>>>> +static struct blkio_policy_node *
>>>> +blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev)
>>>> +{
>>>> + struct blkio_policy_node *pn;
>>>> +
>>>> + list_for_each_entry(pn, &blkcg->policy_list, node) {
>>>> + if (pn->dev == dev)
>>>> + return pn;
>>>> + }
>>>> +
>>>> + return NULL;
>>>> +}
>>>> +
>>>> struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
>>>> {
>>>> return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
>>>> @@ -128,6 +155,7 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
>>>> struct blkio_group *blkg;
>>>> struct hlist_node *n;
>>>> struct blkio_policy_type *blkiop;
>>>> + struct blkio_policy_node *pn;
>>>>
>>>> if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
>>>> return -EINVAL;
>>>> @@ -136,7 +164,13 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
>>>> spin_lock(&blkio_list_lock);
>>>> spin_lock_irq(&blkcg->lock);
>>>> blkcg->weight = (unsigned int)val;
>>>> +
>>>> hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
>>>> + pn = blkio_policy_search_node(blkcg, blkg->dev);
>>>> +
>>>> + if (pn)
>>>> + continue;
>>>> +
>>>> list_for_each_entry(blkiop, &blkio_list, list)
>>>> blkiop->ops.blkio_update_group_weight_fn(blkg,
>>>> blkcg->weight);
>>>> @@ -178,15 +212,208 @@ SHOW_FUNCTION_PER_GROUP(dequeue);
>>>>
>>>> #ifdef CONFIG_DEBUG_BLK_CGROUP
>>>> void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
>>>> - unsigned long dequeue)
>>>> + unsigned long dequeue)
>>>> {
>>>> blkg->dequeue += dequeue;
>>>> }
>>>> EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
>>>> #endif
>>>>
>>>> +static int blkio_check_dev_num(dev_t dev)
>>>> +{
>>>> + int part = 0;
>>>> + struct gendisk *disk;
>>>> +
>>>> + disk = get_gendisk(dev, &part);
>>>> + if (!disk || part)
>>>> + return -ENODEV;
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int blkio_policy_parse_and_set(char *buf,
>>>> + struct blkio_policy_node *newpn)
>>>> +{
>>>> + char *s[4], *p, *major_s = NULL, *minor_s = NULL;
>>>> + int ret;
>>>> + unsigned long major, minor, temp;
>>>> + int i = 0;
>>>> + dev_t dev;
>>>> +
>>>> + memset(s, 0, sizeof(s));
>>>> +
>>>> + while ((p = strsep(&buf, " ")) != NULL) {
>>>> + if (!*p)
>>>> + continue;
>>>> +
>>>> + s[i++] = p;
>>>> +
>>>> + /* Prevent from inputing too many things */
>>>> + if (i == 3)
>>>> + break;
>>>> + }
>>>> +
>>>> + if (i != 2)
>>>> + return -EINVAL;
>>>> +
>>>> + p = strsep(&s[0], ":");
>>>> + if (p != NULL)
>>>> + major_s = p;
>>>> + else
>>>> + return -EINVAL;
>>>> +
>>>> + minor_s = s[0];
>>>> + if (!minor_s)
>>>> + return -EINVAL;
>>>> +
>>>> + ret = strict_strtoul(major_s, 10, &major);
>>>> + if (ret)
>>>> + return -EINVAL;
>>>> +
>>>> + ret = strict_strtoul(minor_s, 10, &minor);
>>>> + if (ret)
>>>> + return -EINVAL;
>>>> +
>>>> + dev = MKDEV(major, minor);
>> I am not quite sure if exposing a mojor,minor number is the best
>> interface that can be exposed to user space. How about actual disk
>> names like sda, sdb, .. etc? The only problem I see there is that it
>> seems tricky to get to these disk names from within the block layer.
>> "struct request_queue" has a pointer to backing_dev which has a device
>> from which we can get major,minor. But in order to get to disk name,
>> we would have to call get_gendisk which can hold a semaphore. Is this
>> the reason for us going with major,minor as a user interface to
>> specify a disk? I bet there are good reasons for us not keeping a
>> pointer to "struct gendisk" from "struct request_queue". If we could
>> keep that pointer, our user interface could be very easily modified to
>> be the disk name like sda, sdb, etc.
>
> That's a good question. Why not use device names instead of device
> numbers? From user's perspective, device names will be more intutive
> to use.
>
> At the same time, will it look odd to handle devices with their names as WWID.
>
> /dev/mapper/3600508b400105df70000e000026f0000
>
> Though I see that there is an alternate way to address the same device
> like /dev/dm-2 etc.
>
> So from user's perspective I think it will be more intutive to handle
> disk names instead of numbers.
>
> Gui, did you forsee issues in implementing disk names?
Hi Vivek,
>From the implementation of view, we need a device number as a key in blkio_policy_node,
if using device name as user interface, i can't figure out a way to retirve the
corresponding device number by means of device name (like sda, not "/dev/sda").
Jens, is there any method to handle this?
Another cgroup subsystem "device" cgroup also make use of device number as user interface,
I guess the reason is the same.
Thanks,
Gui
>
> Thanks
> Vivek
>
>
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