netdev - Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

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Message-ID: <CD773D0D.7614%blourdel@juniper.net>
Date:	Tue, 26 Mar 2013 11:51:07 +0000
From:	Benoit Lourdelet <blourdel@...iper.net>
To:	Stephen Hemminger <stephen@...workplumber.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...ntu.com>
Subject: Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

Hello,

I re-tested with the patch and got the following results on a 32x 2Ghz
core system.

# veth 	add 	delete
1000 	36 	34
3000 	259 	137
4000 	462 	195
5000 	729     N/A

The script to create is the following :
for i in `seq 1 5000`; do
	sudo ip link add type veth
Done


The script to delete:
for d in /sys/class/net/veth*; do
	ip link del `basename $d` 2>/dev/null || true
Done

There is a very good improvement in deletion.



iproute2 does not seems to be well multithread as I get time divided by a
factor of 2 with a 8x  3.2 Ghz core system.

I don¹t know if that is the improvement you expected ?

Would the iproute2 redesign you mentioned help improve performance even
further ?


As a reference : Iproute2 baseline w/o patch:

# veth 	add 	delete

1000 	57 	70
2000 	193 	250
3000 	435 	510
4000 	752 	824
5000 	1123 	1185

Regards

Benoit




On 22/03/2013 23:27, "Stephen Hemminger" <stephen@...workplumber.org>
wrote:

>The whole ifindex map is a design mistake at this point.
>Better off to do a lazy cache or something like that.
>
>
>On Fri, Mar 22, 2013 at 3:23 PM, Eric W. Biederman
><ebiederm@...ssion.com> wrote:
>>
>> Because ip link add, set, and delete map the interface name to the
>> interface index by dumping all of the interfaces before performing
>> their respective commands.  Operations that should be constant time
>> slow down when lots of network interfaces are in use.  Resulting
>> in O(N^2) time to work with O(N) devices.
>>
>> Make the work that iproute does constant time by passing the interface
>> name to the kernel instead.
>>
>> In small scale testing on my system this shows dramatic performance
>> increases of ip link add from 120s to just 11s to add 5000 network
>> devices.  And from longer than I cared to wait to just 58s to delete
>> all of those interfaces again.
>>
>> Cc: Serge Hallyn <serge.hallyn@...ntu.com>
>> Reported-by: Benoit Lourdelet <blourdel@...iper.net>
>> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>> ---
>>
>> I think I am bungling the case where people specify an ifindex as ifNNNN
>> but does anyone care?
>>
>>  ip/iplink.c |   19 +------------------
>>  1 files changed, 1 insertions(+), 18 deletions(-)
>>
>> diff --git a/ip/iplink.c b/ip/iplink.c
>> index ad33611..6dffbf0 100644
>> --- a/ip/iplink.c
>> +++ b/ip/iplink.c
>> @@ -533,8 +533,6 @@ static int iplink_modify(int cmd, unsigned int
>>flags, int argc, char **argv)
>>                 }
>>         }
>>
>> -       ll_init_map(&rth);
>> -
>>         if (!(flags & NLM_F_CREATE)) {
>>                 if (!dev) {
>>                         fprintf(stderr, "Not enough information:
>>\"dev\" "
>> @@ -542,27 +540,12 @@ static int iplink_modify(int cmd, unsigned int
>>flags, int argc, char **argv)
>>                         exit(-1);
>>                 }
>>
>> -               req.i.ifi_index = ll_name_to_index(dev);
>> -               if (req.i.ifi_index == 0) {
>> -                       fprintf(stderr, "Cannot find device \"%s\"\n",
>>dev);
>> -                       return -1;
>> -               }
>> +               name = dev;
>>         } else {
>>                 /* Allow "ip link add dev" and "ip link add name" */
>>                 if (!name)
>>                         name = dev;
>>
>> -               if (link) {
>> -                       int ifindex;
>> -
>> -                       ifindex = ll_name_to_index(link);
>> -                       if (ifindex == 0) {
>> -                               fprintf(stderr, "Cannot find device
>>\"%s\"\n",
>> -                                       link);
>> -                               return -1;
>> -                       }
>> -                       addattr_l(&req.n, sizeof(req), IFLA_LINK,
>>&ifindex, 4);
>> -               }
>>         }
>>
>>         if (name) {
>> --
>> 1.7.5.4
>>
>


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