![Eric Dumazet](/assets/img/avatar_default.png)
This patch puts mostly read only data in the right section (read_mostly), to help sharing of these data between CPUS without memory ping pongs. On one of my production machine, tcp_statistics was sitting in a heavily modified cache line, so *every* SNMP update had to force a reload. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
372 lines
8 KiB
C
372 lines
8 KiB
C
/* flow.c: Generic flow cache.
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*
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* Copyright (C) 2003 Alexey N. Kuznetsov (kuznet@ms2.inr.ac.ru)
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* Copyright (C) 2003 David S. Miller (davem@redhat.com)
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/jhash.h>
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#include <linux/interrupt.h>
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#include <linux/mm.h>
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#include <linux/random.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/smp.h>
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#include <linux/completion.h>
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#include <linux/percpu.h>
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#include <linux/bitops.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <net/flow.h>
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#include <asm/atomic.h>
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#include <asm/semaphore.h>
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struct flow_cache_entry {
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struct flow_cache_entry *next;
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u16 family;
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u8 dir;
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struct flowi key;
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u32 genid;
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void *object;
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atomic_t *object_ref;
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};
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atomic_t flow_cache_genid = ATOMIC_INIT(0);
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static u32 flow_hash_shift;
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#define flow_hash_size (1 << flow_hash_shift)
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static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };
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#define flow_table(cpu) (per_cpu(flow_tables, cpu))
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static kmem_cache_t *flow_cachep __read_mostly;
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static int flow_lwm, flow_hwm;
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struct flow_percpu_info {
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int hash_rnd_recalc;
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u32 hash_rnd;
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int count;
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} ____cacheline_aligned;
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static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };
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#define flow_hash_rnd_recalc(cpu) \
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(per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
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#define flow_hash_rnd(cpu) \
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(per_cpu(flow_hash_info, cpu).hash_rnd)
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#define flow_count(cpu) \
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(per_cpu(flow_hash_info, cpu).count)
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static struct timer_list flow_hash_rnd_timer;
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#define FLOW_HASH_RND_PERIOD (10 * 60 * HZ)
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struct flow_flush_info {
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atomic_t cpuleft;
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struct completion completion;
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};
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static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };
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#define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))
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static void flow_cache_new_hashrnd(unsigned long arg)
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{
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int i;
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for_each_cpu(i)
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flow_hash_rnd_recalc(i) = 1;
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flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
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add_timer(&flow_hash_rnd_timer);
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}
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static void __flow_cache_shrink(int cpu, int shrink_to)
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{
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struct flow_cache_entry *fle, **flp;
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int i;
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for (i = 0; i < flow_hash_size; i++) {
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int k = 0;
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flp = &flow_table(cpu)[i];
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while ((fle = *flp) != NULL && k < shrink_to) {
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k++;
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flp = &fle->next;
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}
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while ((fle = *flp) != NULL) {
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*flp = fle->next;
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if (fle->object)
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atomic_dec(fle->object_ref);
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kmem_cache_free(flow_cachep, fle);
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flow_count(cpu)--;
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}
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}
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}
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static void flow_cache_shrink(int cpu)
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{
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int shrink_to = flow_lwm / flow_hash_size;
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__flow_cache_shrink(cpu, shrink_to);
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}
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static void flow_new_hash_rnd(int cpu)
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{
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get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
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flow_hash_rnd_recalc(cpu) = 0;
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__flow_cache_shrink(cpu, 0);
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}
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static u32 flow_hash_code(struct flowi *key, int cpu)
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{
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u32 *k = (u32 *) key;
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return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
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(flow_hash_size - 1));
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}
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#if (BITS_PER_LONG == 64)
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typedef u64 flow_compare_t;
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#else
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typedef u32 flow_compare_t;
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#endif
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extern void flowi_is_missized(void);
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/* I hear what you're saying, use memcmp. But memcmp cannot make
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* important assumptions that we can here, such as alignment and
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* constant size.
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*/
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static int flow_key_compare(struct flowi *key1, struct flowi *key2)
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{
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flow_compare_t *k1, *k1_lim, *k2;
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const int n_elem = sizeof(struct flowi) / sizeof(flow_compare_t);
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if (sizeof(struct flowi) % sizeof(flow_compare_t))
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flowi_is_missized();
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k1 = (flow_compare_t *) key1;
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k1_lim = k1 + n_elem;
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k2 = (flow_compare_t *) key2;
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do {
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if (*k1++ != *k2++)
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return 1;
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} while (k1 < k1_lim);
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return 0;
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}
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void *flow_cache_lookup(struct flowi *key, u16 family, u8 dir,
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flow_resolve_t resolver)
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{
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struct flow_cache_entry *fle, **head;
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unsigned int hash;
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int cpu;
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local_bh_disable();
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cpu = smp_processor_id();
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fle = NULL;
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/* Packet really early in init? Making flow_cache_init a
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* pre-smp initcall would solve this. --RR */
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if (!flow_table(cpu))
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goto nocache;
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if (flow_hash_rnd_recalc(cpu))
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flow_new_hash_rnd(cpu);
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hash = flow_hash_code(key, cpu);
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head = &flow_table(cpu)[hash];
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for (fle = *head; fle; fle = fle->next) {
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if (fle->family == family &&
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fle->dir == dir &&
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flow_key_compare(key, &fle->key) == 0) {
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if (fle->genid == atomic_read(&flow_cache_genid)) {
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void *ret = fle->object;
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if (ret)
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atomic_inc(fle->object_ref);
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local_bh_enable();
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return ret;
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}
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break;
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}
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}
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if (!fle) {
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if (flow_count(cpu) > flow_hwm)
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flow_cache_shrink(cpu);
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fle = kmem_cache_alloc(flow_cachep, SLAB_ATOMIC);
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if (fle) {
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fle->next = *head;
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*head = fle;
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fle->family = family;
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fle->dir = dir;
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memcpy(&fle->key, key, sizeof(*key));
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fle->object = NULL;
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flow_count(cpu)++;
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}
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}
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nocache:
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{
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void *obj;
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atomic_t *obj_ref;
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resolver(key, family, dir, &obj, &obj_ref);
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if (fle) {
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fle->genid = atomic_read(&flow_cache_genid);
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if (fle->object)
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atomic_dec(fle->object_ref);
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fle->object = obj;
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fle->object_ref = obj_ref;
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if (obj)
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atomic_inc(fle->object_ref);
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}
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local_bh_enable();
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return obj;
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}
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}
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static void flow_cache_flush_tasklet(unsigned long data)
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{
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struct flow_flush_info *info = (void *)data;
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int i;
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int cpu;
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cpu = smp_processor_id();
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for (i = 0; i < flow_hash_size; i++) {
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struct flow_cache_entry *fle;
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fle = flow_table(cpu)[i];
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for (; fle; fle = fle->next) {
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unsigned genid = atomic_read(&flow_cache_genid);
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if (!fle->object || fle->genid == genid)
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continue;
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fle->object = NULL;
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atomic_dec(fle->object_ref);
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}
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}
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if (atomic_dec_and_test(&info->cpuleft))
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complete(&info->completion);
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}
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static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
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static void flow_cache_flush_per_cpu(void *data)
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{
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struct flow_flush_info *info = data;
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int cpu;
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struct tasklet_struct *tasklet;
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cpu = smp_processor_id();
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tasklet = flow_flush_tasklet(cpu);
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tasklet->data = (unsigned long)info;
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tasklet_schedule(tasklet);
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}
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void flow_cache_flush(void)
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{
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struct flow_flush_info info;
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static DECLARE_MUTEX(flow_flush_sem);
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/* Don't want cpus going down or up during this. */
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lock_cpu_hotplug();
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down(&flow_flush_sem);
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atomic_set(&info.cpuleft, num_online_cpus());
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init_completion(&info.completion);
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local_bh_disable();
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smp_call_function(flow_cache_flush_per_cpu, &info, 1, 0);
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flow_cache_flush_tasklet((unsigned long)&info);
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local_bh_enable();
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wait_for_completion(&info.completion);
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up(&flow_flush_sem);
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unlock_cpu_hotplug();
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}
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static void __devinit flow_cache_cpu_prepare(int cpu)
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{
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struct tasklet_struct *tasklet;
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unsigned long order;
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for (order = 0;
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(PAGE_SIZE << order) <
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(sizeof(struct flow_cache_entry *)*flow_hash_size);
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order++)
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/* NOTHING */;
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flow_table(cpu) = (struct flow_cache_entry **)
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__get_free_pages(GFP_KERNEL, order);
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if (!flow_table(cpu))
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panic("NET: failed to allocate flow cache order %lu\n", order);
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memset(flow_table(cpu), 0, PAGE_SIZE << order);
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flow_hash_rnd_recalc(cpu) = 1;
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flow_count(cpu) = 0;
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tasklet = flow_flush_tasklet(cpu);
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tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static int flow_cache_cpu(struct notifier_block *nfb,
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unsigned long action,
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void *hcpu)
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{
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if (action == CPU_DEAD)
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__flow_cache_shrink((unsigned long)hcpu, 0);
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return NOTIFY_OK;
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}
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#endif /* CONFIG_HOTPLUG_CPU */
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static int __init flow_cache_init(void)
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{
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int i;
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flow_cachep = kmem_cache_create("flow_cache",
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sizeof(struct flow_cache_entry),
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0, SLAB_HWCACHE_ALIGN,
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NULL, NULL);
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if (!flow_cachep)
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panic("NET: failed to allocate flow cache slab\n");
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flow_hash_shift = 10;
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flow_lwm = 2 * flow_hash_size;
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flow_hwm = 4 * flow_hash_size;
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init_timer(&flow_hash_rnd_timer);
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flow_hash_rnd_timer.function = flow_cache_new_hashrnd;
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flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
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add_timer(&flow_hash_rnd_timer);
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for_each_cpu(i)
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flow_cache_cpu_prepare(i);
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hotcpu_notifier(flow_cache_cpu, 0);
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return 0;
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}
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module_init(flow_cache_init);
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EXPORT_SYMBOL(flow_cache_genid);
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EXPORT_SYMBOL(flow_cache_lookup);
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