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Date: Fri, 07 Mar 2008 13:56:32 +0900
From: Li Zefan <lizf@...fujitsu.com>
To: balbir@...ux.vnet.ibm.com
CC: Paul Menage <menage@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Pavel Emelianov <xemul@...nvz.org>,
Hugh Dickins <hugh@...itas.com>,
Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
linux-kernel@...r.kernel.org, taka@...inux.co.jp,
linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] Add cgroup support for enabling controllers at boot time
Balbir Singh wrote:
> Li Zefan wrote:
>> Balbir Singh wrote:
>>> From: Paul Menage <menage@...gle.com>
>>>
>>> The effects of cgroup_disable=foo are:
>>>
>>> - foo doesn't show up in /proc/cgroups
>>> - foo isn't auto-mounted if you mount all cgroups in a single hierarchy
>>> - foo isn't visible as an individually mountable subsystem
>>>
>>> As a result there will only ever be one call to foo->create(), at init
>>> time; all processes will stay in this group, and the group will never
>>> be mounted on a visible hierarchy. Any additional effects (e.g. not
>>> allocating metadata) are up to the foo subsystem.
>>>
>>> This doesn't handle early_init subsystems (their "disabled" bit isn't
>>> set be, but it could easily be extended to do so if any of the early_init
>>> systems wanted it - I think it would just involve some nastier parameter
>>> processing since it would occur before the command-line argument parser
>>> had been run.
>>>
>>> [Balbir added Documentation/kernel-parameters updates]
>>>
>>> Signed-off-by: Paul Menage <menage@...gle.com>
>>> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
>>> ---
>>>
>>> Documentation/kernel-parameters.txt | 4 ++++
>>> include/linux/cgroup.h | 1 +
>>> kernel/cgroup.c | 27 +++++++++++++++++++++++++--
>>> 3 files changed, 30 insertions(+), 2 deletions(-)
>>>
>>> diff -puN include/linux/cgroup.h~cgroup_disable include/linux/cgroup.h
>>> --- linux-2.6.25-rc4/include/linux/cgroup.h~cgroup_disable
>>> 2008-03-06 12:19:38.000000000 +0530
>>> +++ linux-2.6.25-rc4-balbir/include/linux/cgroup.h 2008-03-06
>>> 12:19:38.000000000 +0530
>>> @@ -256,6 +256,7 @@ struct cgroup_subsys {
>>> void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
>>> int subsys_id;
>>> int active;
>>> + int disabled;
>>> int early_init;
>>> #define MAX_CGROUP_TYPE_NAMELEN 32
>>> const char *name;
>>> diff -puN kernel/cgroup.c~cgroup_disable kernel/cgroup.c
>>> --- linux-2.6.25-rc4/kernel/cgroup.c~cgroup_disable 2008-03-06
>>> 12:19:38.000000000 +0530
>>> +++ linux-2.6.25-rc4-balbir/kernel/cgroup.c 2008-03-06
>>> 12:19:38.000000000 +0530
>>> @@ -782,7 +782,14 @@ static int parse_cgroupfs_options(char *
>>> if (!*token)
>>> return -EINVAL;
>>> if (!strcmp(token, "all")) {
>>> - opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1;
>>> + /* Add all non-disabled subsystems */
>>> + int i;
>>> + opts->subsys_bits = 0;
>>> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
>>> + struct cgroup_subsys *ss = subsys[i];
>>> + if (!ss->disabled)
>>> + opts->subsys_bits |= 1ul << i;
>>> + }
>>> } else if (!strcmp(token, "noprefix")) {
>>> set_bit(ROOT_NOPREFIX, &opts->flags);
>>> } else if (!strncmp(token, "release_agent=", 14)) {
>>> @@ -800,7 +807,8 @@ static int parse_cgroupfs_options(char *
>>> for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
>>> ss = subsys[i];
>>> if (!strcmp(token, ss->name)) {
>>> - set_bit(i, &opts->subsys_bits);
>>> + if (!ss->disabled)
>>> + set_bit(i, &opts->subsys_bits);
>>> break;
>>> }
>>> }
>>> @@ -2604,6 +2612,8 @@ static int proc_cgroupstats_show(struct
>>> mutex_lock(&cgroup_mutex);
>>> for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
>>> struct cgroup_subsys *ss = subsys[i];
>>> + if (ss->disabled)
>>> + continue;
>>> seq_printf(m, "%s\t%lu\t%d\n",
>>> ss->name, ss->root->subsys_bits,
>>> ss->root->number_of_cgroups);
>>> @@ -3010,3 +3020,16 @@ static void cgroup_release_agent(struct
>>> spin_unlock(&release_list_lock);
>>> mutex_unlock(&cgroup_mutex);
>>> }
>>> +
>>> +static int __init cgroup_disable(char *str)
>>> +{
>>> + int i;
>>> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
>>> + struct cgroup_subsys *ss = subsys[i];
>>> + if (!strcmp(str, ss->name)) {
>>> + ss->disabled = 1;
>>> + break;
>>> + }
>>> + }
>>> +}
>>> +__setup("cgroup_disable=", cgroup_disable);
>>> diff -puN Documentation/kernel-parameters.txt~cgroup_disable
>>> Documentation/kernel-parameters.txt
>>> ---
>>> linux-2.6.25-rc4/Documentation/kernel-parameters.txt~cgroup_disable
>>> 2008-03-06 17:57:32.000000000 +0530
>>> +++ linux-2.6.25-rc4-balbir/Documentation/kernel-parameters.txt
>>> 2008-03-06 18:00:32.000000000 +0530
>>> @@ -383,6 +383,10 @@ and is between 256 and 4096 characters.
>>> ccw_timeout_log [S390]
>>> See Documentation/s390/CommonIO for details.
>>>
>>> + cgroup_disable= [KNL] Enable disable a particular controller
>>> + Format: {name of the controller}
>>> + See /proc/cgroups for a list of compiled controllers
>>> +
>> The changelog of this patch:
>> - foo doesn't show up in /proc/cgroups
>>
>> So a disabled subsystem won't show up in /proc/cgroups. In a previous
>> mail, I asked whether it will be useful to print out the disable bit
>> in /proc/cgroups, so we can distinguish a subsystem from disaled and
>> not-compiled.
>
> Hi, Li,
>
> That is a good idea, but can that come in later? We need to get the boot option
> in, so that users can decide at boot time whether they want the page_container
> overhead. I'll send out another set of patches to add that feature or work
> with Paul to see what he thinks about it.
>
I'm not requiring this to be done in this patch. :)
But my exact meaning here is this sentence is confusing:
See /proc/cgroups for a list of compiled controllers
It seems it is telling people that /proc/cgroups shows not only enabled
but also disabled cgroup subsystems.
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