Re: [ckrm-tech] [RFC][PATCH 3/7] UBC: ub context and inheritance

[Matt Helsley <matthltc@us.ibm.com>]

On Wed, 2006-08-16 at 19:38 +0400, Kirill Korotaev wrote:
> Contains code responsible for setting UB on task,
> it's inheriting and setting host context in interrupts.
> 
> Task references three beancounters:
>   1. exec_ub  current context. all resources are
>               charged to this beancounter.

nit: 2-3 below seem to contradict "all". If you mean "the rest" then
perhaps you ought to reorder these:

1. task_ub ...
2. fork_sub ...
3. exec_ub Current context. Resources not charged to task_ub
           or fork_sub are charged to this beancounter.

>   2. task_ub  beancounter to which task_struct is
>               charged itself.

Is task_ub frequently the parent beancounter of exec_ub? If it's always
the parent then perhaps the one or more of these _ub fields in the task
struct are not necessary. Also in that case keeping copies of the
"parent" user_beancounter pointers in the task_beancounters would seem
bug-prone -- if the hierarchy of beancounters changes then these would
need to be changed too.

>   3. fork_sub beancounter which is inherited by
>               task's children on fork

Is this frequently the same as exec_ub?

> Signed-Off-By: Pavel Emelianov <xemul@sw.ru>
> Signed-Off-By: Kirill Korotaev <dev@sw.ru>
> 
> ---
>  include/linux/sched.h   |    5 +++++
>  include/ub/task.h       |   42 ++++++++++++++++++++++++++++++++++++++++++
>  kernel/fork.c           |   21 ++++++++++++++++-----
>  kernel/irq/handle.c     |    9 +++++++++
>  kernel/softirq.c        |    8 ++++++++
>  kernel/ub/Makefile      |    1 +
>  kernel/ub/beancounter.c |    4 ++++
>  kernel/ub/misc.c        |   34 ++++++++++++++++++++++++++++++++++
>  8 files changed, 119 insertions(+), 5 deletions(-)
> 
> --- ./include/linux/sched.h.ubfork	2006-07-17 17:01:12.000000000 +0400
> +++ ./include/linux/sched.h	2006-07-31 16:01:54.000000000 +0400
> @@ -81,6 +81,8 @@ struct sched_param {
>  #include <linux/timer.h>
>  #include <linux/hrtimer.h>
>  
> +#include <ub/task.h>
> +
>  #include <asm/processor.h>
>  
>  struct exec_domain;
> @@ -997,6 +999,9 @@ struct task_struct {
>  	spinlock_t delays_lock;
>  	struct task_delay_info *delays;
>  #endif
> +#ifdef CONFIG_USER_RESOURCE
> +	struct task_beancounter	task_bc;
> +#endif
>  };
>  
>  static inline pid_t process_group(struct task_struct *tsk)
> --- ./include/ub/task.h.ubfork	2006-07-28 18:53:52.000000000 +0400
> +++ ./include/ub/task.h	2006-08-01 15:26:08.000000000 +0400
> @@ -0,0 +1,42 @@
> +/*
> + *  include/ub/task.h
> + *
> + *  Copyright (C) 2006 OpenVZ. SWsoft Inc
> + *
> + */
> +
> +#ifndef __UB_TASK_H_
> +#define __UB_TASK_H_
> +
> +#include <linux/config.h>
> +
> +struct user_beancounter;
> +
> +struct task_beancounter {
> +	struct user_beancounter *exec_ub;
> +	struct user_beancounter *task_ub;
> +	struct user_beancounter *fork_sub;
> +};
> +
> +#ifdef CONFIG_USER_RESOURCE
> +#define get_exec_ub()		(current->task_bc.exec_ub)
> +#define set_exec_ub(newub)			\
> +	({					\
> +		 struct user_beancounter *old;	\
> +		 struct task_beancounter *tbc;	\
> +		 tbc = &current->task_bc;	\
> +		 old = tbc->exec_ub;		\
> +		 tbc->exec_ub = newub;		\
> +		 old;				\
> +	 })
> +

How about making these static inlines?

> +int ub_task_charge(struct task_struct *parent, struct task_struct *new);
> +void ub_task_uncharge(struct task_struct *tsk);
> +
> +#else /* CONFIG_USER_RESOURCE */
> +#define get_exec_ub()		(NULL)
> +#define set_exec_ub(__ub)	(NULL)
> +#define ub_task_charge(p, t)	(0)
> +#define ub_task_uncharge(t)	do { } while (0)
> +#endif /* CONFIG_USER_RESOURCE */
> +#endif /* __UB_TASK_H_ */
> --- ./kernel/irq/handle.c.ubirq	2006-07-10 12:39:20.000000000 +0400
> +++ ./kernel/irq/handle.c	2006-08-01 12:39:34.000000000 +0400
> @@ -16,6 +16,9 @@
>  #include <linux/interrupt.h>
>  #include <linux/kernel_stat.h>
>  
> +#include <ub/beancounter.h>
> +#include <ub/task.h>
> +
>  #include "internals.h"
>  
>  /**
> @@ -166,6 +169,9 @@ fastcall unsigned int __do_IRQ(unsigned 
>  	struct irq_desc *desc = irq_desc + irq;
>  	struct irqaction *action;
>  	unsigned int status;
> +	struct user_beancounter *ub;
> +
> +	ub = set_exec_ub(&ub0);

Perhaps a comment: "/* Don't charge resources gained in interrupts to current */ 

>  	kstat_this_cpu.irqs[irq]++;
>  	if (CHECK_IRQ_PER_CPU(desc->status)) {
> @@ -178,6 +184,8 @@ fastcall unsigned int __do_IRQ(unsigned 
>  			desc->chip->ack(irq);
>  		action_ret = handle_IRQ_event(irq, regs, desc->action);
>  		desc->chip->end(irq);
> +
> +		(void) set_exec_ub(ub);
>  		return 1;
>  	}
>  
> @@ -246,6 +254,7 @@ out:
>  	desc->chip->end(irq);
>  	spin_unlock(&desc->lock);
>  
> +	(void) set_exec_ub(ub);


Seems like a WARN_ON() would be appropriate rather than ignoring the
return code.

>  	return 1;
>  }
>  
> --- ./kernel/softirq.c.ubirq	2006-07-17 17:01:12.000000000 +0400
> +++ ./kernel/softirq.c	2006-08-01 12:40:44.000000000 +0400
> @@ -18,6 +18,9 @@
>  #include <linux/rcupdate.h>
>  #include <linux/smp.h>
>  
> +#include <ub/beancounter.h>
> +#include <ub/task.h>
> +
>  #include <asm/irq.h>
>  /*
>     - No shared variables, all the data are CPU local.
> @@ -191,6 +194,9 @@ asmlinkage void __do_softirq(void)
>  	__u32 pending;
>  	int max_restart = MAX_SOFTIRQ_RESTART;
>  	int cpu;
> +	struct user_beancounter *ub;
> +
> +	ub = set_exec_ub(&ub0);

Perhaps add the same comment...

>  	pending = local_softirq_pending();
>  	account_system_vtime(current);
> @@ -229,6 +235,8 @@ restart:
>  
>  	account_system_vtime(current);
>  	_local_bh_enable();
> +
> +	(void) set_exec_ub(ub);

.. and the same WARN_ON.

>  }
>  
>  #ifndef __ARCH_HAS_DO_SOFTIRQ
> --- ./kernel/fork.c.ubfork	2006-07-17 17:01:12.000000000 +0400
> +++ ./kernel/fork.c	2006-08-01 12:58:36.000000000 +0400
> @@ -46,6 +46,8 @@
>  #include <linux/delayacct.h>
>  #include <linux/taskstats_kern.h>
>  
> +#include <ub/task.h>
> +
>  #include <asm/pgtable.h>
>  #include <asm/pgalloc.h>
>  #include <asm/uaccess.h>
> @@ -102,6 +104,7 @@ static kmem_cache_t *mm_cachep;
>  
>  void free_task(struct task_struct *tsk)
>  {
> +	ub_task_uncharge(tsk);
>  	free_thread_info(tsk->thread_info);
>  	rt_mutex_debug_task_free(tsk);
>  	free_task_struct(tsk);
> @@ -162,18 +165,19 @@ static struct task_struct *dup_task_stru
>  
>  	tsk = alloc_task_struct();
>  	if (!tsk)
> -		return NULL;
> +		goto out;
>  
>  	ti = alloc_thread_info(tsk);
> -	if (!ti) {
> -		free_task_struct(tsk);
> -		return NULL;
> -	}
> +	if (!ti)
> +		goto out_tsk;
>  
>  	*tsk = *orig;
>  	tsk->thread_info = ti;
>  	setup_thread_stack(tsk, orig);
>  
> +	if (ub_task_charge(orig, tsk))
> +		goto out_ti;
> +
>  	/* One for us, one for whoever does the "release_task()" (usually parent) */
>  	atomic_set(&tsk->usage,2);
>  	atomic_set(&tsk->fs_excl, 0);
> @@ -180,6 +184,13 @@ static struct task_struct *dup_task_stru
>  #endif
>  	tsk->splice_pipe = NULL;
>  	return tsk;
> +
> +out_ti:
> +	free_thread_info(ti);
> +out_tsk:
> +	free_task_struct(tsk);
> +out:
> +	return NULL;

Ugh. This is starting to look like copy_process(). Any reason you
couldn't move the bean counter bits to copy_process() instead?

>  }
>  
>  #ifdef CONFIG_MMU
> --- ./kernel/ub/Makefile.ubcore	2006-08-03 16:24:56.000000000 +0400
> +++ ./kernel/ub/Makefile	2006-08-01 11:08:39.000000000 +0400
> @@ -5,3 +5,4 @@
>  #
>  
>  obj-$(CONFIG_USER_RESOURCE) += beancounter.o
> +obj-$(CONFIG_USER_RESOURCE) += misc.o
> --- ./kernel/ub/beancounter.c.ubcore	2006-07-28 13:07:44.000000000 +0400
> +++ ./kernel/ub/beancounter.c	2006-08-03 16:14:17.000000000 +0400
> @@ -395,6 +395,10 @@
>  	spin_lock_init(&ub_hash_lock);
>  	slot = &ub_hash[ub_hash_fun(ub->ub_uid)];
>  	hlist_add_head(&ub->hash, slot);
> +
> +	current->task_bc.exec_ub = ub;
> +	current->task_bc.task_ub = get_beancounter(ub);
> +	current->task_bc.fork_sub = get_beancounter(ub);
>  }
>  
>  void __init ub_init_late(void)
> --- ./kernel/ub/misc.c.ubfork	2006-07-31 16:23:44.000000000 +0400
> +++ ./kernel/ub/misc.c	2006-07-31 16:28:47.000000000 +0400
> @@ -0,0 +1,34 @@
> +/*
> + * kernel/ub/misc.c
> + *
> + * Copyright (C) 2006 OpenVZ. SWsoft Inc.
> + *
> + */
> +
> +#include <linux/sched.h>
> +
> +#include <ub/beancounter.h>
> +#include <ub/task.h>
> +
> +int ub_task_charge(struct task_struct *parent, struct task_struct *new)
> +{

parent could be derived from new if you move the charge to copy_process
instead of dup_task_struct.

> +	struct task_beancounter *old_bc;
> +	struct task_beancounter *new_bc;
> +	struct user_beancounter *ub;
> +
> +	old_bc = &parent->task_bc;
> +	new_bc = &new->task_bc;
> +
> +	ub = old_bc->fork_sub;
> +	new_bc->exec_ub = get_beancounter(ub);
> +	new_bc->task_ub = get_beancounter(ub);
> +	new_bc->fork_sub = get_beancounter(ub);
> +	return 0;
> +}
> +
> +void ub_task_uncharge(struct task_struct *tsk)
> +{
> +	put_beancounter(tsk->task_bc.exec_ub);
> +	put_beancounter(tsk->task_bc.task_ub);
> +	put_beancounter(tsk->task_bc.fork_sub);
> +}
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