Re: [PATCH] dev: use name hash for dev_seq_ops

Instead of using the dev->next chain and trying to resync at each call to
dev_seq_start, use the name hash, keeping the bucket and the offset 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 <redacted>
---
 net/core/dev.c |   84 ++++++++++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 69 insertions(+), 15 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 70ecb86..6edbcc5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -4041,6 +4041,60 @@ static int dev_ifconf(struct net *net, char __user *arg)
 }
 
 #ifdef CONFIG_PROC_FS
+
+#define BUCKET_SPACE (32 - NETDEV_HASHBITS)
+
+struct dev_iter_state {
+	struct seq_net_private p;
+	unsigned int pos; /* bucket << BUCKET_SPACE + offset */
+};
+
+#define get_bucket(x) ((x) >> BUCKET_SPACE)
+#define get_offset(x) ((x) & ((1 << BUCKET_SPACE) - 1))
+#define set_bucket_offset(b, o) ((b) << BUCKET_SPACE | (o))
+
+static inline struct net_device *dev_from_same_bucket(struct seq_file *seq)