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[NET]: Define infrastructure to keep 'inuse' changes in an efficent SMP/NUMA way.

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"struct proto" currently uses an array stats[NR_CPUS] to track change on
'inuse' sockets per protocol.

If NR_CPUS is big, this means we use a big memory area for this.
Moreover, all this memory area is located on a single node on NUMA
machines, increasing memory pressure on the boot node.

In this patch, I tried to :

- Keep a fast !CONFIG_SMP implementation
- Keep a fast CONFIG_SMP implementation for often used protocols
(tcp,udp,raw,...)
- Introduce a NUMA efficient implementation

Some helper macros are defined in include/net/sock.h
These macros take into account CONFIG_SMP

If a "struct proto" is declared without using DEFINE_PROTO_INUSE /
REF_PROTO_INUSE
macros, it will automatically use a default implementation, using a
dynamically allocated percpu zone.
This default implementation will be NUMA efficient, but might use 32/64
bytes per possible cpu
because of current alloc_percpu() implementation.
However it still should be better than previous implementation based on
stats[NR_CPUS] field.

When a "struct proto" is changed to use the new macros, we use a single
static "int" percpu variable,
lowering the memory and cpu costs, still preserving NUMA efficiency.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2007-11-05 23:38:39 -08:00 • committed by David S. Miller
parent 91781004b9
commit 286ab3d460
4 changed files with 112 additions and 37 deletions
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63
include/net/sock.h
View file

@ -560,6 +560,14 @@ struct proto {
void (*unhash)(struct sock *sk);
int (*get_port)(struct sock *sk, unsigned short snum);
#ifdef CONFIG_SMP
/* Keeping track of sockets in use */
void (*inuse_add)(struct proto *prot, int inc);
int (*inuse_getval)(const struct proto *prot);
int *inuse_ptr;
#else
int inuse;
#endif
/* Memory pressure */
void (*enter_memory_pressure)(void);
atomic_t *memory_allocated; /* Current allocated memory. */
@ -592,12 +600,38 @@ struct proto {
#ifdef SOCK_REFCNT_DEBUG
atomic_t socks;
#endif
struct {
int inuse;
u8 __pad[SMP_CACHE_BYTES - sizeof(int)];
} stats[NR_CPUS];
};
/*
* Special macros to let protos use a fast version of inuse{get|add}
* using a static percpu variable per proto instead of an allocated one,
* saving one dereference.
* This might be changed if/when dynamic percpu vars become fast.
*/
#ifdef CONFIG_SMP
# define DEFINE_PROTO_INUSE(NAME) \
static DEFINE_PER_CPU(int, NAME##_inuse); \
static void NAME##_inuse_add(struct proto *prot, int inc) \
{ \
__get_cpu_var(NAME##_inuse) += inc; \
} \
\
static int NAME##_inuse_getval(const struct proto *prot)\
{ \
int res = 0, cpu; \
\
for_each_possible_cpu(cpu) \
res += per_cpu(NAME##_inuse, cpu); \
return res; \
}
# define REF_PROTO_INUSE(NAME) \
.inuse_add = NAME##_inuse_add, \
.inuse_getval = NAME##_inuse_getval,
#else
# define DEFINE_PROTO_INUSE(NAME)
# define REF_PROTO_INUSE(NAME)
#endif
extern int proto_register(struct proto *prot, int alloc_slab);
extern void proto_unregister(struct proto *prot);
@ -629,12 +663,29 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
/* Called with local bh disabled */
static __inline__ void sock_prot_inc_use(struct proto *prot)
{
prot->stats[smp_processor_id()].inuse++;
#ifdef CONFIG_SMP
prot->inuse_add(prot, 1);
#else
prot->inuse++;
#endif
}
static __inline__ void sock_prot_dec_use(struct proto *prot)
{
prot->stats[smp_processor_id()].inuse--;
#ifdef CONFIG_SMP
prot->inuse_add(prot, -1);
#else
prot->inuse--;
#endif
}
static __inline__ int sock_prot_inuse(struct proto *proto)
{
#ifdef CONFIG_SMP
return proto->inuse_getval(proto);
#else
return proto->inuse;
#endif
}
/* With per-bucket locks this operation is not-atomic, so that