netdev - Re: [PATCH 3/4] flowcache: make struct flow_cache_percpu::hash_rnd

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Message-ID: <CACVxJT9sC2Zmqd5XBQQ0b0vGaEPaH1MiursFP-dJxxg5PURM3g@mail.gmail.com>
Date:   Wed, 22 Mar 2017 13:38:05 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 3/4] flowcache: make struct flow_cache_percpu::hash_rnd_recalc
 bool

On Wed, Mar 22, 2017 at 5:09 AM, David Miller <davem@...emloft.net> wrote:
> From: Alexey Dobriyan <adobriyan@...il.com>
> Date: Mon, 20 Mar 2017 01:27:43 +0300
>
>> ->hash_rnd_recalc is only used in boolean context.
>>
>> Space savings on x86_64 come from the fact that "MOV rm8, imm8" is
>> shorter than "MOV rm32, imm32" by at least 3 bytes.
>>
>>       add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-10 (-10)
>>       function                                     old     new   delta
>>       flow_cache_new_hashrnd                       166     163      -3
>>       flow_cache_cpu_up_prep                       171     168      -3
>>       flow_cache_lookup                           1148    1144      -4
>>       Total: Before=170822872, After=170822862, chg -0.00%
>>
>> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
>
> I agree with Eric Dumazet that we might have atomicity issues in the
> future because of this change.
>
> Why don't you drop this and resubmit just the other 3 patches which
> seem to be much less controversial?

Sure, bool patch was last minute change.