[Devel] Re: [RFC][PATCH 2/7] UBC: core (structures, API)

[Rohit Seth]

On Wed, 2006-08-16 at 19:37 +0400, Kirill Korotaev wrote:
> Core functionality and interfaces of UBC:
> find/create beancounter, initialization,
> charge/uncharge of resource, core objects' declarations.
> 
> Basic structures:
>   ubparm           - resource description
>   user_beancounter - set of resources, id, lock
> 
> Signed-Off-By: Pavel Emelianov <xemul at sw.ru>
> Signed-Off-By: Kirill Korotaev <dev at sw.ru>
> 
> ---
>  include/ub/beancounter.h |  157 ++++++++++++++++++
>  init/main.c              |    4
>  kernel/Makefile          |    1
>  kernel/ub/Makefile       |    7
>  kernel/ub/beancounter.c  |  398 +++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 567 insertions(+)
> 
> --- /dev/null	2006-07-18 14:52:43.075228448 +0400
> +++ ./include/ub/beancounter.h	2006-08-10 14:58:27.000000000 +0400
> @@ -0,0 +1,157 @@
> +/*
> + *  include/ub/beancounter.h
> + *
> + *  Copyright (C) 2006 OpenVZ. SWsoft Inc
> + *
> + */
> +
> +#ifndef _LINUX_BEANCOUNTER_H
> +#define _LINUX_BEANCOUNTER_H
> +
> +/*
> + *	Resource list.
> + */
> +
> +#define UB_RESOURCES	0
> +
> +struct ubparm {
> +	/*
> +	 * A barrier over which resource allocations are failed gracefully.
> +	 * e.g. if the amount of consumed memory is over the barrier further
> +	 * sbrk() or mmap() calls fail, the existing processes are not killed.
> +	 */
> +	unsigned long	barrier;
> +	/* hard resource limit */
> +	unsigned long	limit;
> +	/* consumed resources */
> +	unsigned long	held;
> +	/* maximum amount of consumed resources through the last period */
> +	unsigned long	maxheld;
> +	/* minimum amount of consumed resources through the last period */
> +	unsigned long	minheld;
> +	/* count of failed charges */
> +	unsigned long	failcnt;
> +};

What is the difference between barrier and limit. They both sound like
hard limits.  No?

> +
> +/*
> + * Kernel internal part.
> + */
> +
> +#ifdef __KERNEL__
> +
> +#include <linux/config.h>
> +#include <linux/spinlock.h>
> +#include <linux/list.h>
> +#include <asm/atomic.h>
> +
> +/*
> + * UB_MAXVALUE is essentially LONG_MAX declared in a cross-compiling safe form.
> + */
> +#define UB_MAXVALUE	( (1UL << (sizeof(unsigned long)*8-1)) - 1)
> +
> +
> +/*
> + *	Resource management structures
> + * Serialization issues:
> + *   beancounter list management is protected via ub_hash_lock
> + *   task pointers are set only for current task and only once
> + *   refcount is managed atomically
> + *   value and limit comparison and change are protected by per-ub spinlock
> + */
> +
> +struct user_beancounter
> +{
> +	atomic_t		ub_refcount;
> +	spinlock_t		ub_lock;
> +	uid_t			ub_uid;

Why uid?  Will it be possible to club processes belonging to different
users to same bean counter.

> +	struct hlist_node	hash;
> +
> +	struct user_beancounter	*parent;
> +	void			*private_data;
> +

What are the above two fields used for?

> +	/* resources statistics and settings */
> +	struct ubparm		ub_parms[UB_RESOURCES];
> +};
> +

I presume UB_RESOURCES value is going to change as different resources
start getting tracked.

I think something like configfs should be used for user interface.  It
automatically presents the right interfaces to user land (based on
kernel implementation).  And you wouldn't need any changes in glibc etc.


-rohit