linux-kernel - Re: [PATCH] net: optimize cmpxchg in ip_idents

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Message-Id: <20200116.042722.153124126288244814.davem@davemloft.net>
Date:   Thu, 16 Jan 2020 04:27:22 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     zhangshaokun@...ilicon.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        jinyuqi@...wei.com, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        edumazet@...gle.com, guoyang2@...wei.com
Subject: Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve

From: Shaokun Zhang <zhangshaokun@...ilicon.com>
Date: Wed, 15 Jan 2020 11:23:40 +0800

> From: Yuqi Jin <jinyuqi@...wei.com>
> 
> atomic_try_cmpxchg is called instead of atomic_cmpxchg that can reduce
> the access number of the global variable @p_id in the loop. Let's
> optimize it for performance.
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
> Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Yang Guo <guoyang2@...wei.com>
> Signed-off-by: Yuqi Jin <jinyuqi@...wei.com>
> Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>

I doubt this makes any measurable improvement in performance.

If you can document a specific measurable improvement under
a useful set of circumstances for real usage, then put those
details into the commit message and resubmit.

Otherwise, I'm not applying this, sorry.