LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Pavel Emelyanov <xemul@openvz.org>
To: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linux Containers <containers@lists.osdl.org>,
	Paul Menage <menage@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][DOCUMENTATION] Minimal controller code for a quick	start
Date: Fri, 08 Feb 2008 12:28:26 +0300	[thread overview]
Message-ID: <47AC20BA.4070906@openvz.org> (raw)
In-Reply-To: <20080207204704.GA16628@sergelap.ibm.com>

Serge E. Hallyn wrote:
> Quoting Pavel Emelyanov (xemul@openvz.org):
>> The Documentation/cgroups.txt file contains the info on how
>> to write some controller for cgroups subsystem, but even with
>> this, one need to write quite a lot of code before developing
>> the core (or copy-n-paste it from some other place).
>>
>> I propose to put this minimal controller into Documentation
>> directory to let people copy-n-paste a) from a known place and 
>> b) a small piece of code.
>>
>> Besides, many people learn better reading an example rather
>> than/along with a document.
>>
>> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
> 
> Actually I thought that was the main point of kernel/cgroup_debug.c?

This one doesn't show how to use generic read/write for files,
but a bit more advanced read_uint/write_uiant, it doesn't declare
its own cgroup with extra fields and doesn't show how to get the
one from task.

Hmm... This one is even more minimal than my :)

> -serge
> 
>> ---
>>
>> diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt
>> index 42d7c4c..66068dc 100644
>> --- a/Documentation/cgroups.txt
>> +++ b/Documentation/cgroups.txt
>> @@ -531,6 +531,9 @@ and root cgroup. Currently this will only involve movement between
>>  the default hierarchy (which never has sub-cgroups) and a hierarchy
>>  that is being created/destroyed (and hence has no sub-cgroups).
>>
>> +For a quick start you may want to look at the
>> +Documentation/controllers/example.c file.
>> +
>>  4. Questions
>>  ============
>>
>> diff --git a/Documentation/controllers/example.c b/Documentation/controllers/example.c
>> new file mode 100644
>> index 0000000..4a73c77
>> --- /dev/null
>> +++ b/Documentation/controllers/example.c
>> @@ -0,0 +1,134 @@
>> +/*
>> + * Documentation/controllers/example.c - A simple controller
>> + *
>> + * Copy and make s/foo/$SUBSYS_NAME/g in it to get a minimal
>> + * working code. Don't forget to add a SUBSYS(foo) line in the
>> + * include/linux/cgroup_subsys.h file.
>> + *
>> + */
>> +
>> +#include <linux/cgroup.h>
>> +
>> +/*
>> + * the foo main structure - it is used to store any info, that
>> + * is required from the group of tasks
>> + */
>> +
>> +struct foo_cgroup {
>> +	/*
>> +	 * put your fields here
>> +	 */
>> +
>> +	struct cgroup_subsys_state css;
>> +
>> +	/*
>> +	 * ... or/and here
>> +	 */
>> +};
>> +
>> +/*
>> + * helpers to get the foo_cgroup from a task and a control group
>> + */
>> +
>> +static inline struct foo_cgroup *foo_from_css(struct cgroup_subsys_state *css)
>> +{
>> +	return container_of(css, struct foo_cgroup, css);
>> +}
>> +
>> +static inline struct foo_cgroup *foo_from_cgroup(struct cgroup *cg)
>> +{
>> +	return foo_from_css(cgroup_subsys_state(cg, foo_subsys_id));
>> +}
>> +
>> +static inline struct foo_cgroup *foo_from_task(struct task_struct *p)
>> +{
>> +	return foo_from_css(task_subsys_state(p, foo_subsys_id));
>> +}
>> +
>> +/*
>> + * foo files
>> + */
>> +
>> +static ssize_t foo_bar_read(struct cgroup *cg, struct cftype *cft,
>> +		struct file *file, char __user *userbuf,
>> +		size_t nbytes, loff_t *ppos)
>> +{
>> +	struct foo_cgroup *foo;
>> +
>> +	foo = foo_from_cgroup(cg);
>> +
>> +	/*
>> +	 * produce some output
>> +	 */
>> +
>> +	return nbytes;
>> +}
>> +
>> +static ssize_t foo_bar_write(struct cgroup *cg, struct cftype *cft,
>> +		struct file *file, const char __user *userbuf,
>> +		size_t nbytes, loff_t *ppos)
>> +{
>> +	struct foo_cgroup *foo;
>> +
>> +	foo = foo_from_cgroup(cg);
>> +
>> +	/*
>> +	 * read and tune the foo
>> +	 */
>> +
>> +	return nbytes;
>> +}
>> +
>> +static struct cftype foo_files[] = {
>> +	{
>> +		.name = "bar",
>> +		.read = foo_bar_read,
>> +		.write = foo_bar_write,
>> +	},
>> +};
>> +
>> +/*
>> + * foo subsystem basic callbacks
>> + */
>> +
>> +static struct cgroup_subsys_state *foo_create(struct cgroup_subsys *cs,
>> +		struct cgroup *cg)
>> +{
>> +	struct foo_cgroup *foo;
>> +
>> +	foo = kmalloc(sizeof(struct foo_cgroup), GFP_KERNEL);
>> +	if (foo == NULL)
>> +		return NULL;
>> +
>> +	/*
>> +	 * initialize your fields
>> +	 */
>> +
>> +	return &foo->css;
>> +}
>> +
>> +static void foo_destroy(struct cgroup_subsys *cs, struct cgroup *cg)
>> +{
>> +	struct foo_cgroup *foo;
>> +
>> +	foo = foo_from_cgroup(cg);
>> +
>> +	/*
>> +	 * clean your fields
>> +	 */
>> +
>> +	kfree(foo);
>> +}
>> +
>> +static int foo_populate(struct cgroup_subsys *cs, struct cgroup *cg)
>> +{
>> +	return cgroup_add_files(cg, cs, foo_files, ARRAY_SIZE(foo_files));
>> +}
>> +
>> +struct cgroup_subsys foo_subsys = {
>> +	.name = "foo",
>> +	.subsys_id = foo_subsys_id,
>> +	.create = foo_create,
>> +	.destroy = foo_destroy,
>> +	.populate = foo_populate,
>> +};
>> _______________________________________________
>> Containers mailing list
>> Containers@lists.linux-foundation.org
>> https://lists.linux-foundation.org/mailman/listinfo/containers
> 


      reply	other threads:[~2008-02-08  9:37 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-07 15:37 Pavel Emelyanov
2008-02-07 20:28 ` Peter Zijlstra
2008-02-07 20:49   ` Paul Menage
2008-02-07 20:52     ` Peter Zijlstra
2008-02-07 20:50   ` Serge E. Hallyn
2008-02-07 20:45 ` Paul Menage
2008-02-08  8:09   ` Pavel Emelyanov
2008-02-07 20:47 ` Serge E. Hallyn
2008-02-08  9:28   ` Pavel Emelyanov [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=47AC20BA.4070906@openvz.org \
    --to=xemul@openvz.org \
    --cc=akpm@linux-foundation.org \
    --cc=containers@lists.osdl.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=menage@google.com \
    --cc=serue@us.ibm.com \
    --subject='Re: [PATCH][DOCUMENTATION] Minimal controller code for a quick	start' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).