Subject: Re: [net-next-2.6 PATCH] net: fast consecutive name allocation

From: Eric Dumazet <[email-masked]>
Date: Fri, 13 Nov 2009 07:12:35 +0100

Octavian Purdila a écrit :
> On Friday 13 November 2009 07:01:14 you wrote:
>> This patch speeds up the network device name allocation for the case
>> where a significant number of devices of the same type are created
>> consecutively.
>>
>> Tests performed on a PPC750 @ 800Mhz machine with per device sysctl
>> and sysfs entries disabled:
>>
>> Without the patch           With the patch
>>
>> real    0m 43.43s	    real    0m 0.49s
>> user    0m 0.00s	    user    0m 0.00s
>> sys     0m 43.43s	    sys     0m 0.48s
>>
> 
> Oops, pasting root prompts (e.g. # modprobe ....) directly into the git commit message is not a good idea :) Here it is again, with the full commit message.
> 
> [net-next-2.6 PATCH] net: fast consecutive name allocation
> 
> This patch speeds up the network device name allocation for the case
> where a significant number of devices of the same type are created
> consecutively.
> 
> Tests performed on a PPC750 @ 800Mhz machine with per device sysctl
> and sysfs entries disabled:
> 
> $ time insmod /lib/modules/dummy.ko numdummies=8000
> 
> Without the patch           With the patch
> 
> real    0m 43.43s	    real    0m 0.49s
> user    0m 0.00s	    user    0m 0.00s
> sys     0m 43.43s	    sys     0m 0.48s
> 
> Signed-off-by: Octavian Purdila <[email-masked]>
> ---

Honestly I dont like this bloat.

Changing dummy.c is trivial, and you can allocate 100.000.000 dummies if you want now :)

I not tested yet this patch but here it is :

[PATCH] dummy: Allow more than 32768 dummies

And speedup name allocation : O(N) instead of O(N^2)

Signed-off-by: Eric Dumazet <[email-masked]>
---
 drivers/net/dummy.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/dummy.c b/drivers/net/dummy.c
index 37dcfdc..f600c4c 100644
--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -107,12 +107,14 @@ static struct rtnl_link_ops dummy_link_ops __read_mostly = {
 module_param(numdummies, int, 0);
 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
 
-static int __init dummy_init_one(void)
+static int __init dummy_init_one(int i)
 {
 	struct net_device *dev_dummy;
 	int err;
+	char name[IFNAMSIZ];
 
-	dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
+	snprintf(name, IFNAMSIZ, "dummy%d", i);
+	dev_dummy = alloc_netdev(0, name, dummy_setup);
 	if (!dev_dummy)
 		return -ENOMEM;
 
@@ -139,7 +141,7 @@ static int __init dummy_init_module(void)
 	err = __rtnl_link_register(&dummy_link_ops);
 
 	for (i = 0; i < numdummies && !err; i++)
-		err = dummy_init_one();
+		err = dummy_init_one(i);
 	if (err < 0)
 		__rtnl_link_unregister(&dummy_link_ops);
 	rtnl_unlock();