netdev - Re: [PATCH] drivers/net/b44: Change to non-atomic bit operations

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Message-Id: <20191224.161826.37676943451935844.davem@davemloft.net>
Date:   Tue, 24 Dec 2019 16:18:26 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     fenghua.yu@...el.com
Cc:     michael.chan@...adcom.com, netdev@...r.kernel.org,
        tglx@...utronix.de, luto@...nel.org, peterz@...radead.org,
        tony.luck@...el.com, David.Laight@...LAB.COM,
        ravi.v.shankar@...el.com
Subject: Re: [PATCH] drivers/net/b44: Change to non-atomic bit operations

From: Fenghua Yu <fenghua.yu@...el.com>
Date: Fri, 20 Dec 2019 15:29:11 -0800

> On x86, accessing data across two cache lines in one atomic bit
> operation (aka split lock) can take over 1000 cycles.

This happens during configuration of WOL, nobody cares that the atomic
operations done in this function take 1000 cycles each.

I'm not applying this patch.  It is gratuitous, and the commit message
talks about "performance" considuations (cycle counts) that completely
don't matter here.

If you are merely just arbitrarily trying to remove locked atomic
operations across the tree for it's own sake, then you should be
completely honest about that in your commit message.