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Date: Fri, 07 Mar 2008 10:07:18 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: Li Zefan <lizf@...fujitsu.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
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.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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