Re: purpose of the skb head pool

[Christoph Hellwig <hch@lst.de>]

On Tue, Apr 29, 2003 at 06:12:49AM -0700, David S. Miller wrote:
>    Robert's first reply on this subject had it attached..
>    
> I deleted it, can someone resend me a copy?
> 
> When I ask for a patch, it usually means that I've
> /dev/null'd the entire thread already.

Lazy bastard.. ;)


--- linux/net/core/skbuff.c.030428	2003-04-01 13:24:14.000000000 +0200
+++ linux/net/core/skbuff.c	2003-04-28 16:53:54.000000000 +0200
@@ -20,7 +20,7 @@
  *		Ray VanTassle	:	Fixed --skb->lock in free
  *		Alan Cox	:	skb_copy copy arp field
  *		Andi Kleen	:	slabified it.
+ *		Robert Olsson	:	Removed skb_head_pool
  *
  *	NOTE:
  *		The __skb_ routines should be called with interrupts
@@ -64,15 +64,8 @@
 #include <asm/uaccess.h>
 #include <asm/system.h>
 
-int sysctl_hot_list_len = 128;
-
 static kmem_cache_t *skbuff_head_cache;
 
-static union {
-	struct sk_buff_head	list;
-	char			pad[SMP_CACHE_BYTES];
-} skb_head_pool[NR_CPUS];
-
 /*
  *	Keep out-of-line to prevent kernel bloat.
  *	__builtin_return_address is not used because it is not always
@@ -110,44 +103,6 @@
 	BUG();
 }
 
-static __inline__ struct sk_buff *skb_head_from_pool(void)
-{
-	struct sk_buff_head *list;
-	struct sk_buff *skb = NULL;
-	unsigned long flags;
-
-	local_irq_save(flags);
-
-	list = &skb_head_pool[smp_processor_id()].list;
-
-	if (skb_queue_len(list))
-		skb = __skb_dequeue(list);
-
-	local_irq_restore(flags);
-	return skb;
-}
-
-static __inline__ void skb_head_to_pool(struct sk_buff *skb)
-{
-	struct sk_buff_head *list;
-	unsigned long flags;
-
-	local_irq_save(flags);
-
-	list = &skb_head_pool[smp_processor_id()].list;
-
-	if (skb_queue_len(list) < sysctl_hot_list_len) {
-		__skb_queue_head(list, skb);
-		local_irq_restore(flags);
-
-		return;
-	}
-
-	local_irq_restore(flags);
-	kmem_cache_free(skbuff_head_cache, skb);
-}
-
-
 /* 	Allocate a new skbuff. We do this ourselves so we can fill in a few
  *	'private' fields and also do memory statistics to find all the
  *	[BEEP] leaks.
@@ -182,13 +137,10 @@
 	}
 
 	/* Get the HEAD */
-	skb = skb_head_from_pool();
-	if (!skb) {
-		skb = kmem_cache_alloc(skbuff_head_cache,
+	skb = kmem_cache_alloc(skbuff_head_cache,
 				       gfp_mask & ~__GFP_DMA);
 		if (!skb)
 			goto out;
-	}
 
 	/* Get the DATA. Size must match skb_add_mtu(). */
 	size = SKB_DATA_ALIGN(size);
@@ -207,7 +159,7 @@
 out:
 	return skb;
 nodata:
-	skb_head_to_pool(skb);
+	kmem_cache_free(skbuff_head_cache, skb);
 	skb = NULL;
 	goto out;
 }
@@ -257,7 +209,7 @@
 void kfree_skbmem(struct sk_buff *skb)
 {
 	skb_release_data(skb);
-	skb_head_to_pool(skb);
+	kmem_cache_free(skbuff_head_cache, skb);
 }
 
 /**
@@ -327,13 +279,10 @@
 
 struct sk_buff *skb_clone(struct sk_buff *skb, int gfp_mask)
 {
-	struct sk_buff *n = skb_head_from_pool();
+	struct sk_buff *n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
 
-	if (!n) {
-		n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
-		if (!n)
-			return NULL;
-	}
+	if (!n) 
+		return NULL;
 
 #define C(x) n->x = skb->x
 
@@ -1240,7 +1189,4 @@
 					      NULL, NULL);
 	if (!skbuff_head_cache)
 		panic("cannot create skbuff cache");
-
-	for (i = 0; i < NR_CPUS; i++)
-		skb_queue_head_init(&skb_head_pool[i].list);
 }
--- linux/net/core/sysctl_net_core.c.030428	2003-03-24 23:00:18.000000000 +0100
+++ linux/net/core/sysctl_net_core.c	2003-04-28 16:59:05.000000000 +0200
@@ -28,7 +28,6 @@
 
 extern int sysctl_core_destroy_delay;
 extern int sysctl_optmem_max;
-extern int sysctl_hot_list_len;
 
 #ifdef CONFIG_NET_DIVERT
 extern char sysctl_divert_version[];
@@ -150,14 +149,6 @@
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
 	},
-	{
-		.ctl_name	= NET_CORE_HOT_LIST_LENGTH,
-		.procname	= "hot_list_length",
-		.data		= &sysctl_hot_list_len,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= &proc_dointvec
-	},
 #ifdef CONFIG_NET_DIVERT
 	{
 		.ctl_name	= NET_CORE_DIVERT_VERSION,