netdev - [PATCH 3/7] flow: allocate hash table for online cpus only

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Date:	Mon, 29 Mar 2010 17:12:40 +0300
From:	Timo Teras <timo.teras@....fi>
To:	netdev@...r.kernel.org
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Timo Teras <timo.teras@....fi>
Subject: [PATCH 3/7] flow: allocate hash table for online cpus only

Instead of unconditionally allocating hash table for all possible
cpu's, allocate it only for online cpu's and release related
memory if cpu goes down.

Signed-off-by: Timo Teras <timo.teras@....fi>
---
 net/core/flow.c |   43 ++++++++++++++++++++++++++++++-------------
 1 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/net/core/flow.c b/net/core/flow.c
index 1d27ca6..104078d 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -309,36 +309,49 @@ void flow_cache_flush(void)
 	put_online_cpus();
 }
 
-static void __init flow_cache_cpu_prepare(struct flow_cache *fc,
-					  struct flow_cache_percpu *fcp)
+static void __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc,
+					     struct flow_cache_percpu *fcp)
 {
 	fcp->hash_table = (struct flow_cache_entry **)
 		__get_free_pages(GFP_KERNEL|__GFP_ZERO, fc->order);
-	if (!fcp->hash_table)
-		panic("NET: failed to allocate flow cache order %lu\n", fc->order);
-
 	fcp->hash_rnd_recalc = 1;
 	fcp->hash_count = 0;
 	tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
 }
 
-static int flow_cache_cpu(struct notifier_block *nfb,
-			  unsigned long action,
-			  void *hcpu)
+static int __cpuinit flow_cache_cpu(struct notifier_block *nfb,
+				    unsigned long action,
+				    void *hcpu)
 {
 	struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
 	int cpu = (unsigned long) hcpu;
 	struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
 
-	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
-		__flow_cache_shrink(fc, fcp, 0);
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		flow_cache_cpu_prepare(fc, fcp);
+		if (!fcp->hash_table)
+			return NOTIFY_BAD;
+		break;
+	case CPU_UP_CANCELED:
+	case CPU_UP_CANCELED_FROZEN:
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+		if (fcp->hash_table) {
+			__flow_cache_shrink(fc, fcp, 0);
+			free_pages((unsigned long) fcp->hash_table, fc->order);
+			fcp->hash_table = NULL;
+		}
+		break;
+	}
 	return NOTIFY_OK;
 }
 
 static int flow_cache_init(struct flow_cache *fc)
 {
 	unsigned long order;
-	int i;
+	int i, r;
 
 	fc->hash_shift = 10;
 	fc->low_watermark = 2 * flow_cache_hash_size(fc);
@@ -357,8 +370,12 @@ static int flow_cache_init(struct flow_cache *fc)
 	fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
 	add_timer(&fc->rnd_timer);
 
-	for_each_possible_cpu(i)
-		flow_cache_cpu_prepare(fc, per_cpu_ptr(fc->percpu, i));
+	for_each_online_cpu(i) {
+		r = flow_cache_cpu(&fc->hotcpu_notifier,
+				   CPU_UP_PREPARE, (void*) i);
+		if (r != NOTIFY_OK)
+			panic("NET: failed to allocate flow cache order %lu\n", order);
+	}
 
 	fc->hotcpu_notifier = (struct notifier_block){
 		.notifier_call = flow_cache_cpu,
-- 
1.6.3.3

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