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Subject[PATCH] dev: use ifindex hash for dev_seq_ops
Date
Instead of using the dev->next chain and trying to resync at each call to
dev_seq_start, use the ifindex, keeping the last index in seq->private field.

Tests revealed the following results for ifconfig > /dev/null
* 1000 interfaces:
* 0.114s without patch
* 0.089s with patch
* 3000 interfaces:
* 0.489s without patch
* 0.110s with patch
* 5000 interfaces:
* 1.363s without patch
* 0.250s with patch
* 128000 interfaces (other setup):
* ~100s without patch
* ~30s with patch
Signed-off-by: Mihai Maruseac <mmaruseac@ixiacom.com>
---
net/core/dev.c | 55 ++++++++++++++++++++++++++++++++++---------------------
1 files changed, 34 insertions(+), 21 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 70ecb86..ea24445 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4041,6 +4041,37 @@ static int dev_ifconf(struct net *net, char __user *arg)
}

#ifdef CONFIG_PROC_FS
+
+struct dev_iter_state {
+ struct seq_net_private p;
+ int ifindex;
+};
+
+static struct net_device *__dev_seq_next(struct seq_file *seq, loff_t *pos)
+{
+ struct dev_iter_state *state = seq->private;
+ struct net *net = seq_file_net(seq);
+ struct net_device *dev;
+ loff_t off;
+
+ dev = dev_get_by_index_rcu(net, state->ifindex);
+ if (likely(dev))
+ goto found;
+
+ off = 0;
+ for_each_netdev_rcu(net, dev)
+ if (off++ == *pos) {
+ state->ifindex = dev->ifindex;
+ goto found;
+ }
+
+ return NULL;
+found:
+ state->ifindex++;
+ ++*pos;
+ return dev;
+}
+
/*
* This is invoked by the /proc filesystem handler to display a device
* in detail.
@@ -4048,33 +4079,15 @@ static int dev_ifconf(struct net *net, char __user *arg)
void *dev_seq_start(struct seq_file *seq, loff_t *pos)
__acquires(RCU)
{
- struct net *net = seq_file_net(seq);
- loff_t off;
- struct net_device *dev;
-
rcu_read_lock();
if (!*pos)
return SEQ_START_TOKEN;
-
- off = 1;
- for_each_netdev_rcu(net, dev)
- if (off++ == *pos)
- return dev;
-
- return NULL;
+ return __dev_seq_next(seq, pos);
}

void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct net_device *dev = v;
-
- if (v == SEQ_START_TOKEN)
- dev = first_net_device_rcu(seq_file_net(seq));
- else
- dev = next_net_device_rcu(dev);
-
- ++*pos;
- return dev;
+ return __dev_seq_next(seq, pos);
}

void dev_seq_stop(struct seq_file *seq, void *v)
@@ -4173,7 +4186,7 @@ static const struct seq_operations dev_seq_ops = {
static int dev_seq_open(struct inode *inode, struct file *file)
{
return seq_open_net(inode, file, &dev_seq_ops,
- sizeof(struct seq_net_private));
+ sizeof(struct dev_iter_state));
}

static const struct file_operations dev_seq_fops = {
--
1.7.4.1

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