BC proc entries

This page describes proc interface of UBC subsystem.

Old interface

Old interface consisted of 2 (optionally 3) files

user_beancounters

reveals an overall information about resource consumption of each beancounter in system

user_beancounters_sub

reveals information about all beancounters and sub-beancounters in system

user_beancounters_debug

this files is shown if CONFIG_UBC_DEBUG_KMEM option is turned on and shows debugging information about each beancounter. This includes the numbers of

1. objects charged from each slab
2. pages charged
3. vmalloc-ed pages
4. page beancounters
5. etc

New interface

In new interface only user_beancounters entry is left for compatibility with old tools. New entries reside in /proc/bc directory. This directory also contains subdirectories for each beancounter in the system. E.g.

# ls /proc/bc/
0  ioacct_debug  resources
# vzctl  start 101
...
# ls /proc/bc
0  101  ioacct_debug  resources
# ls /proc/bc/101/
ioacct  kmem_debug  resources  vmaux

All new entries that are in /proc/bc shows some overall information about BC subsystem, while entries in /proc/bc/$BCID show per-beancounter info.

Existing general entries

/proc/bc/resources

This entry looks like old user_beancounters entry but

1. it doesn't contain “dummy” resources
2. if new resource is added to BC it will appear in this entry only

/proc/bc/$BCID/resources

This entry shows the same as bc/resources does but for $BCID beancounter only.

/proc/bc/$BCID/vmaux

This entry shows auxiliary resources used in VM accounting.

/proc/bc/$BCID/kmem_debug

This entry is available with CONFIG_UBC_DEBUG_KMEM option set and shows per-beancounter info that was in /proc/user_beancounters_debug before.

Kernel API

Subsystems may add its own entries in /proc/bc or /proc/bc/$BCID. To facilitate this the following API is used in BC sybsystem (declared in include/ub/proc.h).

struct proc_dir_entry *bc_proc_root

This is an entry that corresponds to /proc/bc directory. If a subsystem wishes to report some information that is not per-beancounter it may create entry using this as a parent.

struct bc_proc_entry;

This describes an entry that may show per-beancounter info. This looks like this:

struct bc_proc_entry {
        char *name;
        int (*show)(struct seq_file *, void *);
        struct bc_proc_entry *next;
};

• name is the entry name as it will appear in /proc/bc/$BCID
• show is a callback that is to fill info about particulat beancounter

void bc_register_proc_entry(struct bc_proc_entry *);

This call registers an entry that shows per-beancounter info.

The code that fills info about BC must look like this

static int bc_my_show(struct seq_file *f, void *v)
{
        struct user_beancounter *ub;

        ub = seq_beancounter(f);
        /* dump info into f here */
        return 0;
}
...
static struct bc_proc_entry my_entry = {
        .name = "my_entry",
        .show = bc_my_show,
};

static int __init bc_my_init(void)
{
        bc_register_proc_entry(&my_entry);
        return 0;
}

late_initcall(bc_my_init);

Note: Due to limitations in single_open the struct user_beancounter pointer is not passed as void *v into showing function but must be obtained from seq_file with seq_beancounter