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From: "Paul Menage" <menage@google.com>
To: balbir@in.ibm.com
Cc: akpm@osdl.org, pj@sgi.com, sekharan@us.ibm.com, dev@sw.ru,
	xemul@sw.ru, serue@us.ibm.com, vatsa@in.ibm.com,
	ckrm-tech@lists.sourceforge.net, linux-kernel@vger.kernel.org,
	rohitseth@google.com, mbligh@google.com, winget@google.com,
	containers@lists.osdl.org, devel@openvz.org
Subject: Re: [PATCH 1/1] Fix a panic while mouting containers on powerpc and some other small cleanups (Re: [ckrm-tech] [PATCH 4/6] containers: Simple CPU accounting container subsystem)
Date: Mon, 15 Jan 2007 01:22:16 -0800	[thread overview]
Message-ID: <6599ad830701150122g7156a599t1b3dd3af9f5f821b@mail.gmail.com> (raw)
In-Reply-To: <45AB43B5.3070007@in.ibm.com>

On 1/15/07, Balbir Singh <balbir@in.ibm.com> wrote:
>
> In sched.c, account_user_time() can be called with the task p set to rq->idle.
> Since idle tasks do not belong to any container, this was causing a panic in
> task_ca() in cpu_acct.c.

How come that didn't cause a problem on x86_64? If this is an
inconsistency between architectures then perhaps it ought to be
cleaned up.

Additionally, I think that we should make the idle tasks members of
the root container(s), to remove this special case. (I'm a bit
surprised that they're not already - I thought that the early
container initialization was early enough that the idle tasks hadn't
yet been forked. Is that different on PowerPC?

>
> Multiplying the time by 1000 is not correct in cpuusage_read(). The code
> has been converted to use the correct cputime API.

Thanks.

>
> Add mount/umount callbacks.

I'm not sure I like the mount/unmount callbacks. What exactly are you
trying to gain from them? My intention was that the

cont->subsys[i]->container = cont;

line in container_get_sb() was doing essentially this - i.e. the
container_subsys_state for the root container in a subsystem is
already kept up to date by the container system, and the subsystem can
rely on the "container" field in the container_subsys_state.

Thanks,

Paul

>
> Signed-off-by: Balbir Singh <balbir@in.ibm.com>
> ---
>
>  kernel/cpu_acct.c |   29 +++++++++++++++++++++++------
>  kernel/sched.c    |   17 +++++++++++------
>  2 files changed, 34 insertions(+), 12 deletions(-)
>
> diff -puN kernel/cpu_acct.c~fix-cpuacct-panic-on-mount kernel/cpu_acct.c
> --- linux-2.6.20-rc3/kernel/cpu_acct.c~fix-cpuacct-panic-on-mount       2007-01-15
> 14:23:20.000000000 +0530
> +++ linux-2.6.20-rc3-balbir/kernel/cpu_acct.c   2007-01-15 14:23:20.000000000 +0530
> @@ -22,6 +22,7 @@ struct cpuacct {
>  };
>
>  static struct container_subsys cpuacct_subsys;
> +static struct container *root;
>
>  static inline struct cpuacct *container_ca(struct container *cont)
>  {
> @@ -49,6 +50,16 @@ static void cpuacct_destroy(struct conta
>         kfree(container_ca(cont));
>  }
>
> +static void cpuacct_mount(struct container_subsys *ss, struct container *cont)
> +{
> +       root = cont;
> +}
> +
> +static void cpuacct_umount(struct container_subsys *ss, struct container *cont)
> +{
> +       root = NULL;
> +}
> +
>  static ssize_t cpuusage_read(struct container *cont,
>                              struct cftype *cft,
>                              struct file *file,
> @@ -57,6 +68,7 @@ static ssize_t cpuusage_read(struct cont
>  {
>         struct cpuacct *ca = container_ca(cont);
>         cputime64_t time;
> +       unsigned long time_in_jiffies;
>         char usagebuf[64];
>         char *s = usagebuf;
>
> @@ -64,9 +76,8 @@ static ssize_t cpuusage_read(struct cont
>         time = ca->time;
>         spin_unlock_irq(&ca->lock);
>
> -       time *= 1000;
> -       do_div(time, HZ);
> -       s += sprintf(s, "%llu", (unsigned long long) time);
> +       time_in_jiffies = cputime_to_jiffies(time);
> +       s += sprintf(s, "%llu\n", (unsigned long long) time_in_jiffies);
>
>         return simple_read_from_buffer(buf, nbytes, ppos, usagebuf, s - usagebuf);
>  }
> @@ -83,12 +94,13 @@ static int cpuacct_populate(struct conta
>  }
>
>
> -void cpuacct_charge(struct task_struct *task, cputime_t cputime) {
> +void cpuacct_charge(struct task_struct *task, cputime_t cputime)
> +{
>
>         struct cpuacct *ca;
>         unsigned long flags;
>
> -       if (cpuacct_subsys.subsys_id < 0) return;
> +       if (cpuacct_subsys.subsys_id < 0 || !root) return;
>         rcu_read_lock();
>         ca = task_ca(task);
>         if (ca) {
> @@ -104,13 +116,18 @@ static struct container_subsys cpuacct_s
>         .create = cpuacct_create,
>         .destroy = cpuacct_destroy,
>         .populate = cpuacct_populate,
> +       .mount = cpuacct_mount,
> +       .umount = cpuacct_umount,
>         .subsys_id = -1,
>  };
>
>
>  int __init init_cpuacct(void)
>  {
> -       int id = container_register_subsys(&cpuacct_subsys);
> +       int id;
> +
> +       root = NULL;
> +       id = container_register_subsys(&cpuacct_subsys);
>         return id < 0 ? id : 0;
>  }
>
> diff -puN kernel/sched.c~fix-cpuacct-panic-on-mount kernel/sched.c
> --- linux-2.6.20-rc3/kernel/sched.c~fix-cpuacct-panic-on-mount  2007-01-15
> 14:23:20.000000000 +0530
> +++ linux-2.6.20-rc3-balbir/kernel/sched.c      2007-01-15 14:23:20.000000000 +0530
> @@ -3067,10 +3067,17 @@ void account_user_time(struct task_struc
>  {
>         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
>         cputime64_t tmp;
> +       struct rq *rq = this_rq();
>
>         p->utime = cputime_add(p->utime, cputime);
>
> -       cpuacct_charge(p, cputime);
> +       /*
> +        * On powerpc this routine can be called with p set to the idle
> +        * task of the cpu. idle tasks don't really belong to any
> +        * container.
> +        */
> +       if (p != rq->idle)
> +               cpuacct_charge(p, cputime);
>
>         /* Add user time to cpustat. */
>         tmp = cputime_to_cputime64(cputime);
> @@ -3095,18 +3102,16 @@ void account_system_time(struct task_str
>
>         p->stime = cputime_add(p->stime, cputime);
>
> -       if (p != rq->idle)
> -               cpuacct_charge(p, cputime);
> -
>         /* Add system time to cpustat. */
>         tmp = cputime_to_cputime64(cputime);
>         if (hardirq_count() - hardirq_offset)
>                 cpustat->irq = cputime64_add(cpustat->irq, tmp);
>         else if (softirq_count())
>                 cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
> -       else if (p != rq->idle)
> +       else if (p != rq->idle) {
>                 cpustat->system = cputime64_add(cpustat->system, tmp);
> -       else if (atomic_read(&rq->nr_iowait) > 0)
> +               cpuacct_charge(p, cputime);
> +       } else if (atomic_read(&rq->nr_iowait) > 0)
>                 cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
>         else
>                 cpustat->idle = cputime64_add(cpustat->idle, tmp);
> _
>
>         Balbir Singh
>         Linux Technology Center
>         Bangalore, IBM ISTL
>

  reply	other threads:[~2007-01-15  9:22 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-22 14:14 [PATCH 0/6] containers: Generic Process Containers (V6) Paul Menage
2006-12-22 14:14 ` [PATCH 1/6] containers: Generic container system abstracted from cpusets code Paul Menage
2006-12-30 13:10   ` Eric W. Biederman
2006-12-31  5:17     ` Paul Jackson
2007-01-02 22:15     ` Paul Menage
2006-12-22 14:14 ` [PATCH 2/6] containers: Cpusets hooked into containers Paul Menage
2006-12-22 14:14 ` [PATCH 3/6] containers: Add generic multi-subsystem API to containers Paul Menage
2007-01-10 15:56   ` [ckrm-tech] " Balbir Singh
2007-01-11 22:53     ` Paul Menage
2007-01-12  6:29       ` Balbir Singh
2007-01-12  8:10         ` Paul Menage
2007-01-12  8:22           ` Balbir Singh
2007-01-20 17:27           ` Balbir Singh
2006-12-22 14:14 ` [PATCH 4/6] containers: Simple CPU accounting container subsystem Paul Menage
2007-01-10 14:21   ` [ckrm-tech] " Balbir Singh
2007-01-12  0:33     ` Paul Menage
2007-01-12  6:24       ` Balbir Singh
2007-01-12  8:15         ` Paul Menage
2007-01-12  8:26           ` Balbir Singh
2007-01-12 17:32             ` Paul Menage
2007-01-15  9:01       ` [PATCH 0/1] Add mount/umount callbacks to containers (Re: [ckrm-tech] [PATCH 4/6] containers: Simple CPU accounting container subsystem) Balbir Singh
2007-01-15  9:04         ` [PATCH 1/1] Fix a panic while mouting containers on powerpc and some other small cleanups " Balbir Singh
2007-01-15  9:22           ` Paul Menage [this message]
2007-01-15  9:51             ` [ckrm-tech] [PATCH 1/1] Fix a panic while mouting containers on powerpc and some other small cleanups (Re: " Balbir Singh
2007-01-15 10:01               ` Paul Menage
2007-01-15 10:10                 ` Balbir Singh
2006-12-22 14:14 ` [PATCH 5/6] containers: Resource Groups over generic containers Paul Menage
2006-12-22 14:14 ` [PATCH 6/6] containers: BeanCounters over generic process containers Paul Menage
2006-12-23 19:49   ` Herbert Poetzl
2006-12-24 11:32     ` Paul Menage
2006-12-25 10:16     ` Kirill Korotaev
2006-12-26  0:54       ` Paul Menage
2006-12-25 10:35     ` Pavel Emelianov
2007-01-03 14:43 ` [PATCH 0/6] containers: Generic Process Containers (V6) Serge E. Hallyn
2007-01-05  0:25   ` Paul Menage
2007-01-12 18:42     ` Serge E. Hallyn

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