netdev - Re: [PATCH v1 01/25] net: core: device_rename: Use rwsem instead of a seqcount

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Date:   Tue, 19 May 2020 20:18:19 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>, tglx@...utronix.de
Cc:     stephen@...workplumber.org, a.darwish@...utronix.de,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        paulmck@...nel.org, bigeasy@...utronix.de, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, kuba@...nel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v1 01/25] net: core: device_rename: Use rwsem instead of a
 seqcount



On 5/19/20 7:57 PM, David Miller wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> Date: Wed, 20 May 2020 01:42:30 +0200
> 
>> Stephen Hemminger <stephen@...workplumber.org> writes:
>>> On Wed, 20 May 2020 00:23:48 +0200
>>> Thomas Gleixner <tglx@...utronix.de> wrote:
>>>> No. We did not. -ENOTESTCASE
>>>
>>> Please try, it isn't that hard..
>>>
>>> # time for ((i=0;i<1000;i++)); do ip li add dev dummy$i type dummy; done
>>>
>>> real	0m17.002s
>>> user	0m1.064s
>>> sys	0m0.375s
>>
>> And that solves the incorrectness of the current code in which way?
> 
> You mentioned that there wasn't a test case, he gave you one to try.
> 

I do not think this would ever use device rename, nor netdev_get_name()

None of this stuff is fast path really.

# time for ((i=1;i<1000;i++)); do ip li add dev dummy$i type dummy; done

real	0m1.127s
user	0m0.270s
sys	0m1.039s