netdev - Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount

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Message-ID: <1490021946.16816.54.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 20 Mar 2017 07:59:06 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        David Miller <davem@...emloft.net>, elena.reshetova@...el.com,
        keescook@...omium.org, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kuznet@....inr.ac.ru, jmorris@...ei.org, kaber@...sh.net,
        stephen@...workplumber.org, ishkamiel@...il.com,
        dwindsor@...il.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to
 refcount_t

On Mon, 2017-03-20 at 07:51 -0700, Eric Dumazet wrote:

> atomic_cmpxchg() on PowerPC is horribly more expensive because of the
> added two SYNC instructions.

Although I just saw that refcount was using atomic_cmpxchg_relaxed()

Time to find some documentation (probably missing) or get some specs for
this thing.