linux-kernel - Re: [PATCH v2] refcount: Create unchecked atomic

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Date:   Fri, 9 Jun 2017 06:24:04 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     Davidlohr Bueso <dave@...olabs.net>,
        "Reshetova, Elena" <elena.reshetova@...el.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Eric Biggers <ebiggers3@...il.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "arozansk@...hat.com" <arozansk@...hat.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        Rik van Riel <riel@...hat.com>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v2] refcount: Create unchecked atomic_t implementation

Hi Davidlohr,

On 06/08/2017 10:09 PM, Davidlohr Bueso wrote:
>
> Yes, this would be a prerequisite for ipc; which I initially thought 
> didn't
> take a performance hit.
>
Did you see a regression for ipc?

The fast paths don't use the refcount, it is only used for rare situations:
- GETALL, SETALL for large arrays
- alloc undo

--
     Manfred