Subject: Re: [PATCH, netfilter] NUMA aware ipv4/netfilter/ip_tables.c

From: Eric Dumazet <[email-masked]>
Date: Tue, 20 Sep 2005 11:47:49 +0200

Hi all

Part of the performance problem we have with netfilter is memory allocation is 
not NUMA aware, but 'only' SMP aware (ie each CPU normally touch separate 
cache lines)

Even with small iptables rules, the cost of this misplacement can be high on 
common workloads.

Instead of using one vmalloc() area (located in the node of the iptables 
process), we now vmalloc() an area for each possible CPU, using NUMA policy 
(MPOL_PREFERRED) so that memory should be allocated in the CPU's node if possible.

If the size of ipt_table is small enough (less than one page), we use 
kmalloc_node() instead of vmalloc(), to use less memory (and less TLB entries) 
in small setups.

This patch try to use local node memory in expensive translate_table() 
function (and others), but doesnt bother to bind the task to the current CPU.

Note : I also optimize get_counters(), using a SET_COUNTER() for the first 
cpu, avoiding a memset() and ADD_COUNTER() if SMP on other cpus.

Thank you

Signed-off-by: Eric Dumazet <[email-masked]>
--- linux-2.6.14-rc1.p1/net/ipv4/netfilter/ip_tables.c	2005-09-19 19:56:12.000000000 +0200
+++ linux-2.6.14-rc1/net/ipv4/netfilter/ip_tables.c	2005-09-20 13:41:37.000000000 +0200
@@ -17,6 +17,7 @@
 #include <linux/skbuff.h>
 #include <linux/kmod.h>
 #include <linux/vmalloc.h>
+#include <linux/mempolicy.h>
 #include <linux/netdevice.h>
 #include <linux/module.h>
 #include <linux/tcp.h>
@@ -82,11 +83,6 @@
    context stops packets coming through and allows user context to read
    the counters or update the rules.
 
-   To be cache friendly on SMP, we arrange them like so:
-   [ n-entries ]
-   ... cache-align padding ...
-   [ n-entries ]
-
    Hence the start of any table is given by get_table() below.  */
 
 /* The table itself */
@@ -104,19 +100,14 @@
 	unsigned int underflow[NF_IP_NUMHOOKS];
 
 	/* ipt_entry tables: one per CPU */
-	char entries[0] ____cacheline_aligned;
+	void *entries[NR_CPUS];
 };
 
 static LIST_HEAD(ipt_target);
 static LIST_HEAD(ipt_match);
 static LIST_HEAD(ipt_tables);
 #define ADD_COUNTER(c,b,p) do { (c).bcnt += (b); (c).pcnt += (p); } while(0)
-
-#ifdef CONFIG_SMP
-#define TABLE_OFFSET(t,p) (SMP_ALIGN((t)->size)*(p))
-#else
-#define TABLE_OFFSET(t,p) 0
-#endif
+#define SET_COUNTER(c,b,p) do { (c).bcnt = (b); (c).pcnt = (p); } while(0)
 
 #if 0
 #define down(x) do { printk("DOWN:%u:" #x "\n", __LINE__); down(x); } while(0)
@@ -289,8 +280,7 @@
 
 	read_lock_bh(&table->lock);
 	IP_NF_ASSERT(table->valid_hooks & (1 << hook));
-	table_base = (void *)table->private->entries
-		+ TABLE_OFFSET(table->private, smp_processor_id());
+	table_base = (void *)table->private->entries[smp_processor_id()];
 	e = get_entry(table_base, table->private->hook_entry[hook]);
 
 #ifdef CONFIG_NETFILTER_DEBUG
@@ -562,7 +552,7 @@
 /* Figures out from what hook each rule can be called: returns 0 if
    there are loops.  Puts hook bitmask in comefrom. */
 static int
-mark_source_chains(struct ipt_table_info *newinfo, unsigned int valid_hooks)
+mark_source_chains(struct ipt_table_info *newinfo, unsigned int valid_hooks, void *entry0)
 {
 	unsigned int hook;
 
@@ -571,7 +561,7 @@
 	for (hook = 0; hook < NF_IP_NUMHOOKS; hook++) {
 		unsigned int pos = newinfo->hook_entry[hook];
 		struct ipt_entry *e
-			= (struct ipt_entry *)(newinfo->entries + pos);
+			= (struct ipt_entry *)(entry0 + pos);
 
 		if (!(valid_hooks & (1 << hook)))
 			continue;
@@ -621,13 +611,13 @@
 						goto next;
 
 					e = (struct ipt_entry *)
-						(newinfo->entries + pos);
+						(entry0 + pos);
 				} while (oldpos == pos + e->next_offset);
 
 				/* Move along one */
 				size = e->next_offset;
 				e = (struct ipt_entry *)
-					(newinfo->entries + pos + size);
+					(entry0 + pos + size);
 				e->counters.pcnt = pos;
 				pos += size;
 			} else {
@@ -644,7 +634,7 @@
 					newpos = pos + e->next_offset;
 				}
 				e = (struct ipt_entry *)
-					(newinfo->entries + newpos);
+					(entry0 + newpos);
 				e->counters.pcnt = pos;
 				pos = newpos;
 			}
@@ -854,6 +844,7 @@
 translate_table(const char *name,
 		unsigned int valid_hooks,
 		struct ipt_table_info *newinfo,
+		void *entry0,
 		unsigned int size,
 		unsigned int number,
 		const unsigned int *hook_entries,
@@ -874,11 +865,11 @@
 	duprintf("translate_table: size %u\n", newinfo->size);
 	i = 0;
 	/* Walk through entries, checking offsets. */
-	ret = IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+	ret = IPT_ENTRY_ITERATE(entry0, newinfo->size,
 				check_entry_size_and_hooks,
 				newinfo,
-				newinfo->entries,
-				newinfo->entries + size,
+				entry0,
+				entry0 + size,
 				hook_entries, underflows, &i);
 	if (ret != 0)
 		return ret;
@@ -906,25 +897,24 @@
 		}
 	}
 
-	if (!mark_source_chains(newinfo, valid_hooks))
+	if (!mark_source_chains(newinfo, valid_hooks, entry0))
 		return -ELOOP;
 
 	/* Finally, each sanity check must pass */
 	i = 0;
-	ret = IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+	ret = IPT_ENTRY_ITERATE(entry0, newinfo->size,
 				check_entry, name, size, &i);
 
 	if (ret != 0) {
-		IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+		IPT_ENTRY_ITERATE(entry0, newinfo->size,
 				  cleanup_entry, &i);
 		return ret;
 	}
 
 	/* And one copy for every other CPU */
-	for (i = 1; i < num_possible_cpus(); i++) {
-		memcpy(newinfo->entries + SMP_ALIGN(newinfo->size)*i,
-		       newinfo->entries,
-		       SMP_ALIGN(newinfo->size));
+	for_each_cpu(i) {
+		if (newinfo->entries[i] && newinfo->entries[i] != entry0)
+			memcpy(newinfo->entries[i], entry0, newinfo->size);
 	}
 
 	return ret;
@@ -940,15 +930,12 @@
 
 #ifdef CONFIG_NETFILTER_DEBUG
 	{
-		struct ipt_entry *table_base;
-		unsigned int i;
+		int cpu;
 
-		for (i = 0; i < num_possible_cpus(); i++) {
-			table_base =
-				(void *)newinfo->entries
-				+ TABLE_OFFSET(newinfo, i);
-
-			table_base->comefrom = 0xdead57ac;
+		for_each_cpu(cpu) {
+			struct ipt_entry *table_base = newinfo->entries[cpu];
+			if (table_base)
+				table_base->comefrom = 0xdead57ac;
 		}
 	}
 #endif
@@ -972,6 +959,7 @@
 }
 
 /* Gets counters. */
+#ifdef CONFIG_SMP
 static inline int
 add_entry_to_counter(const struct ipt_entry *e,
 		     struct ipt_counters total[],
@@ -982,22 +970,44 @@
 	(*i)++;
 	return 0;
 }
+#endif
+static inline int
+set_entry_to_counter(const struct ipt_entry *e,
+		     struct ipt_counters total[],
+		     unsigned int *i)
+{
+	SET_COUNTER(total[*i], e->counters.bcnt, e->counters.pcnt);
+
+	(*i)++;
+	return 0;
+}
 
 static void
 get_counters(const struct ipt_table_info *t,
 	     struct ipt_counters counters[])
 {
 	unsigned int cpu;
+	unsigned int curcpu = raw_smp_processor_id();
 	unsigned int i;
 
-	for (cpu = 0; cpu < num_possible_cpus(); cpu++) {
+	i = 0;
+	IPT_ENTRY_ITERATE(t->entries[curcpu],
+			  t->size,
+			  set_entry_to_counter,
+			  counters,
+			  &i);
+#ifdef CONFIG_SMP
+	for_each_cpu(cpu) {
+		if (cpu == curcpu)
+			continue;
 		i = 0;
-		IPT_ENTRY_ITERATE(t->entries + TABLE_OFFSET(t, cpu),
+		IPT_ENTRY_ITERATE(t->entries[cpu],
 				  t->size,
 				  add_entry_to_counter,
 				  counters,
 				  &i);
 	}
+#endif
 }
 
 static int
@@ -1009,6 +1019,7 @@
 	struct ipt_entry *e;
 	struct ipt_counters *counters;
 	int ret = 0;
+	void *loc_cpu_entry;
 
 	/* We need atomic snapshot of counters: rest doesn't change
 	   (other than comefrom, which userspace doesn't care
@@ -1020,13 +1031,17 @@
 		return -ENOMEM;
 
 	/* First, sum counters... */
-	memset(counters, 0, countersize);
 	write_lock_bh(&table->lock);
 	get_counters(table->private, counters);
 	write_unlock_bh(&table->lock);
 
-	/* ... then copy entire thing from CPU 0... */
-	if (copy_to_user(userptr, table->private->entries, total_size) != 0) {
+	/*
+	 * choose the copy that is on our node,
+	 * but dont worry if the scheduler changes the CPU
+	 */
+	loc_cpu_entry = table->private->entries[raw_smp_processor_id()];
+	/* ... then copy entire thing ... */
+	if (copy_to_user(userptr, loc_cpu_entry, total_size) != 0) {
 		ret = -EFAULT;
 		goto free_counters;
 	}
@@ -1038,7 +1053,7 @@
 		struct ipt_entry_match *m;
 		struct ipt_entry_target *t;
 
-		e = (struct ipt_entry *)(table->private->entries + off);
+		e = (struct ipt_entry *)(loc_cpu_entry + off);
 		if (copy_to_user(userptr + off
 				 + offsetof(struct ipt_entry, counters),
 				 &counters[num],
@@ -1107,6 +1122,56 @@
 	return ret;
 }
 
+static void free_table_info(struct ipt_table_info *info)
+{
+	int cpu;
+	for_each_cpu(cpu) {
+		if (info->size <= PAGE_SIZE)
+			kfree(info->entries[cpu]);
+		else
+			vfree(info->entries[cpu]);
+	}
+	kfree(info);
+}
+
+static struct ipt_table_info *alloc_table_info(unsigned int size)
+{
+struct ipt_table_info *newinfo;
+int cpu;
+	newinfo = kzalloc(sizeof(struct ipt_table_info), GFP_KERNEL);
+	if (!newinfo)
+		return NULL;
+	newinfo->size = size;
+	for_each_cpu(cpu) {
+		if (size <= PAGE_SIZE) {
+			newinfo->entries[cpu] = kmalloc_node(size,
+				GFP_KERNEL,
+				cpu_to_node(cpu));
+		} else {
+#ifdef CONFIG_NUMA
+			struct mempolicy *oldpol;
+			struct mempolicy prefnodepolicy = {
+				.refcnt = ATOMIC_INIT(1),
+				.policy = MPOL_PREFERRED,
+				.v.preferred_node = cpu_to_node(cpu),
+			};
+			oldpol = current->mempolicy;
+			current->mempolicy = &prefnodepolicy;
+#endif
+			newinfo->entries[cpu] = vmalloc(size);
+#ifdef CONFIG_NUMA
+			current->mempolicy = oldpol;
+#endif
+		}
+		if (newinfo->entries[cpu] == 0) {
+			free_table_info(newinfo);
+			return NULL;
+		}
+	}
+	return newinfo;
+}
+
+
 static int
 do_replace(void __user *user, unsigned int len)
 {
@@ -1115,6 +1180,7 @@
 	struct ipt_table *t;
 	struct ipt_table_info *newinfo, *oldinfo;
 	struct ipt_counters *counters;
+	void *loc_cpu_entry, *loc_cpu_old_entry;
 
 	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
 		return -EFAULT;
@@ -1127,12 +1193,15 @@
 	if ((SMP_ALIGN(tmp.size) >> PAGE_SHIFT) + 2 > num_physpages)
 		return -ENOMEM;
 
-	newinfo = vmalloc(sizeof(struct ipt_table_info)
-			  + SMP_ALIGN(tmp.size) * num_possible_cpus());
+	newinfo = alloc_table_info(tmp.size);
 	if (!newinfo)
 		return -ENOMEM;
-
-	if (copy_from_user(newinfo->entries, user + sizeof(tmp),
+	/*
+	 * choose the copy that is on our node,
+	 * but dont worry if the scheduler changes the CPU
+	 */
+	loc_cpu_entry = newinfo->entries[raw_smp_processor_id()];
+	if (copy_from_user(loc_cpu_entry, user + sizeof(tmp),
 			   tmp.size) != 0) {
 		ret = -EFAULT;
 		goto free_newinfo;
@@ -1143,10 +1212,9 @@
 		ret = -ENOMEM;
 		goto free_newinfo;
 	}
-	memset(counters, 0, tmp.num_counters * sizeof(struct ipt_counters));
 
 	ret = translate_table(tmp.name, tmp.valid_hooks,
-			      newinfo, tmp.size, tmp.num_entries,
+			      newinfo, loc_cpu_entry, tmp.size, tmp.num_entries,
 			      tmp.hook_entry, tmp.underflow);
 	if (ret != 0)
 		goto free_newinfo_counters;
@@ -1185,8 +1253,9 @@
 	/* Get the old counters. */
 	get_counters(oldinfo, counters);
 	/* Decrease module usage counts and free resource */
-	IPT_ENTRY_ITERATE(oldinfo->entries, oldinfo->size, cleanup_entry,NULL);
-	vfree(oldinfo);
+	loc_cpu_old_entry = oldinfo->entries[raw_smp_processor_id()];
+	IPT_ENTRY_ITERATE(loc_cpu_old_entry, oldinfo->size, cleanup_entry,NULL);
+	free_table_info(oldinfo);
 	if (copy_to_user(tmp.counters, counters,
 			 sizeof(struct ipt_counters) * tmp.num_counters) != 0)
 		ret = -EFAULT;
@@ -1198,11 +1267,11 @@
 	module_put(t->me);
 	up(&ipt_mutex);
  free_newinfo_counters_untrans:
-	IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size, cleanup_entry,NULL);
+	IPT_ENTRY_ITERATE(loc_cpu_entry, newinfo->size, cleanup_entry,NULL);
  free_newinfo_counters:
 	vfree(counters);
  free_newinfo:
-	vfree(newinfo);
+	free_table_info(newinfo);
 	return ret;
 }
 
@@ -1235,6 +1304,7 @@
 	struct ipt_counters_info tmp, *paddc;
 	struct ipt_table *t;
 	int ret = 0;
+	void *loc_cpu_entry;
 
 	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
 		return -EFAULT;
@@ -1264,7 +1334,12 @@
 	}
 
 	i = 0;
-	IPT_ENTRY_ITERATE(t->private->entries,
+	/*
+	 * choose the copy that is on our node,
+	 * but dont worry if the scheduler changes the CPU
+	 */
+	loc_cpu_entry = t->private->entries[raw_smp_processor_id()];
+	IPT_ENTRY_ITERATE(loc_cpu_entry,
 			  t->private->size,
 			  add_counter_to_entry,
 			  paddc->counters,
@@ -1454,29 +1529,39 @@
 {
 	int ret;
 	struct ipt_table_info *newinfo;
-	static struct ipt_table_info bootstrap
-		= { 0, 0, 0, { 0 }, { 0 }, { } };
+	static struct ipt_table_info bootstrap = {
+		.size = 0,
+		.number = 0,
+		.initial_entries = 0,
+		.hook_entry = { 0 },
+		.underflow = { 0 },
+		.entries = {NULL }
+		};
+	void *loc_cpu_entry;
 
-	newinfo = vmalloc(sizeof(struct ipt_table_info)
-			  + SMP_ALIGN(repl->size) * num_possible_cpus());
+	newinfo = alloc_table_info(repl->size);
 	if (!newinfo)
 		return -ENOMEM;
-
-	memcpy(newinfo->entries, repl->entries, repl->size);
+	/*
+	 * choose the copy that is on our node,
+	 * but dont worry if the scheduler changes the CPU
+	 */
+	loc_cpu_entry = newinfo->entries[raw_smp_processor_id()];
+	memcpy(loc_cpu_entry, repl->entries, repl->size);
 
 	ret = translate_table(table->name, table->valid_hooks,
-			      newinfo, repl->size,
+			      newinfo, loc_cpu_entry, repl->size,
 			      repl->num_entries,
 			      repl->hook_entry,
 			      repl->underflow);
 	if (ret != 0) {
-		vfree(newinfo);
+		free_table_info(newinfo);
 		return ret;
 	}
 
 	ret = down_interruptible(&ipt_mutex);
 	if (ret != 0) {
-		vfree(newinfo);
+		free_table_info(newinfo);
 		return ret;
 	}
 
@@ -1505,20 +1590,25 @@
 	return ret;
 
  free_unlock:
-	vfree(newinfo);
+	free_table_info(newinfo);
 	goto unlock;
 }
 
 void ipt_unregister_table(struct ipt_table *table)
 {
+	void *loc_cpu_entry;
 	down(&ipt_mutex);
 	LIST_DELETE(&ipt_tables, table);
 	up(&ipt_mutex);
 
-	/* Decrease module usage counts and free resources */
-	IPT_ENTRY_ITERATE(table->private->entries, table->private->size,
+	/* Decrease module usage counts and free resources
+	 * choose the copy that is on our node,
+	 * but dont worry if the scheduler changes the CPU
+	 */
+	loc_cpu_entry = table->private->entries[raw_smp_processor_id()];
+	IPT_ENTRY_ITERATE(loc_cpu_entry, table->private->size,
 			  cleanup_entry, NULL);
-	vfree(table->private);
+	free_table_info(table->private);
 }
 
 /* Returns 1 if the port is matched by the range, 0 otherwise */