kernel-aes67/include/linux/vmstat.h
Christoph Lameter f8891e5e1f [PATCH] Light weight event counters
The remaining counters in page_state after the zoned VM counter patches
have been applied are all just for show in /proc/vmstat.  They have no
essential function for the VM.

We use a simple increment of per cpu variables.  In order to avoid the most
severe races we disable preempt.  Preempt does not prevent the race between
an increment and an interrupt handler incrementing the same statistics
counter.  However, that race is exceedingly rare, we may only loose one
increment or so and there is no requirement (at least not in kernel) that
the vm event counters have to be accurate.

In the non preempt case this results in a simple increment for each
counter.  For many architectures this will be reduced by the compiler to a
single instruction.  This single instruction is atomic for i386 and x86_64.
 And therefore even the rare race condition in an interrupt is avoided for
both architectures in most cases.

The patchset also adds an off switch for embedded systems that allows a
building of linux kernels without these counters.

The implementation of these counters is through inline code that hopefully
results in only a single instruction increment instruction being emitted
(i386, x86_64) or in the increment being hidden though instruction
concurrency (EPIC architectures such as ia64 can get that done).

Benefits:
- VM event counter operations usually reduce to a single inline instruction
  on i386 and x86_64.
- No interrupt disable, only preempt disable for the preempt case.
  Preempt disable can also be avoided by moving the counter into a spinlock.
- Handling is similar to zoned VM counters.
- Simple and easily extendable.
- Can be omitted to reduce memory use for embedded use.

References:

RFC http://marc.theaimsgroup.com/?l=linux-kernel&m=113512330605497&w=2
RFC http://marc.theaimsgroup.com/?l=linux-kernel&m=114988082814934&w=2
local_t http://marc.theaimsgroup.com/?l=linux-kernel&m=114991748606690&w=2
V2 http://marc.theaimsgroup.com/?t=115014808400007&r=1&w=2
V3 http://marc.theaimsgroup.com/?l=linux-kernel&m=115024767022346&w=2
V4 http://marc.theaimsgroup.com/?l=linux-kernel&m=115047968808926&w=2

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-30 11:25:36 -07:00

216 lines
5.6 KiB
C

#ifndef _LINUX_VMSTAT_H
#define _LINUX_VMSTAT_H
#include <linux/types.h>
#include <linux/percpu.h>
#include <linux/config.h>
#include <linux/mmzone.h>
#include <asm/atomic.h>
#ifdef CONFIG_VM_EVENT_COUNTERS
/*
* Light weight per cpu counter implementation.
*
* Counters should only be incremented and no critical kernel component
* should rely on the counter values.
*
* Counters are handled completely inline. On many platforms the code
* generated will simply be the increment of a global address.
*/
#define FOR_ALL_ZONES(x) x##_DMA, x##_DMA32, x##_NORMAL, x##_HIGH
enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
FOR_ALL_ZONES(PGALLOC),
PGFREE, PGACTIVATE, PGDEACTIVATE,
PGFAULT, PGMAJFAULT,
FOR_ALL_ZONES(PGREFILL),
FOR_ALL_ZONES(PGSTEAL),
FOR_ALL_ZONES(PGSCAN_KSWAPD),
FOR_ALL_ZONES(PGSCAN_DIRECT),
PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL,
PAGEOUTRUN, ALLOCSTALL, PGROTATED,
NR_VM_EVENT_ITEMS
};
struct vm_event_state {
unsigned long event[NR_VM_EVENT_ITEMS];
};
DECLARE_PER_CPU(struct vm_event_state, vm_event_states);
static inline void __count_vm_event(enum vm_event_item item)
{
__get_cpu_var(vm_event_states.event[item])++;
}
static inline void count_vm_event(enum vm_event_item item)
{
get_cpu_var(vm_event_states.event[item])++;
put_cpu();
}
static inline void __count_vm_events(enum vm_event_item item, long delta)
{
__get_cpu_var(vm_event_states.event[item]) += delta;
}
static inline void count_vm_events(enum vm_event_item item, long delta)
{
get_cpu_var(vm_event_states.event[item])++;
put_cpu();
}
extern void all_vm_events(unsigned long *);
extern void vm_events_fold_cpu(int cpu);
#else
/* Disable counters */
#define get_cpu_vm_events(e) 0L
#define count_vm_event(e) do { } while (0)
#define count_vm_events(e,d) do { } while (0)
#define __count_vm_event(e) do { } while (0)
#define __count_vm_events(e,d) do { } while (0)
#define vm_events_fold_cpu(x) do { } while (0)
#endif /* CONFIG_VM_EVENT_COUNTERS */
#define __count_zone_vm_events(item, zone, delta) \
__count_vm_events(item##_DMA + zone_idx(zone), delta)
/*
* Zone based page accounting with per cpu differentials.
*/
extern atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
static inline void zone_page_state_add(long x, struct zone *zone,
enum zone_stat_item item)
{
atomic_long_add(x, &zone->vm_stat[item]);
atomic_long_add(x, &vm_stat[item]);
}
static inline unsigned long global_page_state(enum zone_stat_item item)
{
long x = atomic_long_read(&vm_stat[item]);
#ifdef CONFIG_SMP
if (x < 0)
x = 0;
#endif
return x;
}
static inline unsigned long zone_page_state(struct zone *zone,
enum zone_stat_item item)
{
long x = atomic_long_read(&zone->vm_stat[item]);
#ifdef CONFIG_SMP
if (x < 0)
x = 0;
#endif
return x;
}
#ifdef CONFIG_NUMA
/*
* Determine the per node value of a stat item. This function
* is called frequently in a NUMA machine, so try to be as
* frugal as possible.
*/
static inline unsigned long node_page_state(int node,
enum zone_stat_item item)
{
struct zone *zones = NODE_DATA(node)->node_zones;
return
#ifndef CONFIG_DMA_IS_NORMAL
#if !defined(CONFIG_DMA_IS_DMA32) && BITS_PER_LONG >= 64
zone_page_state(&zones[ZONE_DMA32], item) +
#endif
zone_page_state(&zones[ZONE_NORMAL], item) +
#endif
#ifdef CONFIG_HIGHMEM
zone_page_state(&zones[ZONE_HIGHMEM], item) +
#endif
zone_page_state(&zones[ZONE_DMA], item);
}
extern void zone_statistics(struct zonelist *, struct zone *);
#else
#define node_page_state(node, item) global_page_state(item)
#define zone_statistics(_zl,_z) do { } while (0)
#endif /* CONFIG_NUMA */
#define __add_zone_page_state(__z, __i, __d) \
__mod_zone_page_state(__z, __i, __d)
#define __sub_zone_page_state(__z, __i, __d) \
__mod_zone_page_state(__z, __i,-(__d))
#define add_zone_page_state(__z, __i, __d) mod_zone_page_state(__z, __i, __d)
#define sub_zone_page_state(__z, __i, __d) mod_zone_page_state(__z, __i, -(__d))
static inline void zap_zone_vm_stats(struct zone *zone)
{
memset(zone->vm_stat, 0, sizeof(zone->vm_stat));
}
extern void inc_zone_state(struct zone *, enum zone_stat_item);
#ifdef CONFIG_SMP
void __mod_zone_page_state(struct zone *, enum zone_stat_item item, int);
void __inc_zone_page_state(struct page *, enum zone_stat_item);
void __dec_zone_page_state(struct page *, enum zone_stat_item);
void mod_zone_page_state(struct zone *, enum zone_stat_item, int);
void inc_zone_page_state(struct page *, enum zone_stat_item);
void dec_zone_page_state(struct page *, enum zone_stat_item);
extern void inc_zone_state(struct zone *, enum zone_stat_item);
void refresh_cpu_vm_stats(int);
void refresh_vm_stats(void);
#else /* CONFIG_SMP */
/*
* We do not maintain differentials in a single processor configuration.
* The functions directly modify the zone and global counters.
*/
static inline void __mod_zone_page_state(struct zone *zone,
enum zone_stat_item item, int delta)
{
zone_page_state_add(delta, zone, item);
}
static inline void __inc_zone_page_state(struct page *page,
enum zone_stat_item item)
{
atomic_long_inc(&page_zone(page)->vm_stat[item]);
atomic_long_inc(&vm_stat[item]);
}
static inline void __dec_zone_page_state(struct page *page,
enum zone_stat_item item)
{
atomic_long_dec(&page_zone(page)->vm_stat[item]);
atomic_long_dec(&vm_stat[item]);
}
/*
* We only use atomic operations to update counters. So there is no need to
* disable interrupts.
*/
#define inc_zone_page_state __inc_zone_page_state
#define dec_zone_page_state __dec_zone_page_state
#define mod_zone_page_state __mod_zone_page_state
static inline void refresh_cpu_vm_stats(int cpu) { }
static inline void refresh_vm_stats(void) { }
#endif
#endif /* _LINUX_VMSTAT_H */