From: Stephen Hemminger <stephen@networkplumber.org>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Miller <davem@davemloft.net>,
michael.chan@broadcom.com, netdev@vger.kernel.org,
tglx@linutronix.de, luto@kernel.org, peterz@infradead.org,
tony.luck@intel.com, David.Laight@ACULAB.COM,
ravi.v.shankar@intel.com
Subject: Re: [PATCH] drivers/net/b44: Change to non-atomic bit operations
Date: Wed, 25 Dec 2019 12:24:24 -0800 [thread overview]
Message-ID: <20191225122424.5bc18036@hermes.lan> (raw)
In-Reply-To: <20191225011020.GE241295@romley-ivt3.sc.intel.com>
On Tue, 24 Dec 2019 17:10:20 -0800
Fenghua Yu <fenghua.yu@intel.com> wrote:
> On Tue, Dec 24, 2019 at 04:18:26PM -0800, David Miller wrote:
> > From: Fenghua Yu <fenghua.yu@intel.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.
>
> We are enabling split lock in the kernel (by default):
> https://lkml.org/lkml/2019/12/12/1129
>
> After applying the split lock detection patch, the set_bit() in b44.c
> may cause split lock and kernel dies.
>
> So should I change the commit message to add the above info?
>
> Thanks.
>
> -Fenghua
Why not just make pwol_pattern aligned and choose the right word to do
the operation on?
next prev parent reply other threads:[~2019-12-25 20:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 23:29 [PATCH] drivers/net/b44: Change to non-atomic bit operations Fenghua Yu
2019-12-25 0:18 ` David Miller
2019-12-25 1:10 ` Fenghua Yu
2019-12-25 2:23 ` David Miller
2020-01-02 21:27 ` [Patch v2] drivers/net/b44: Change to non-atomic bit operations on pwol_mask Luck, Tony
2020-01-05 22:22 ` David Miller
2019-12-25 20:24 ` Stephen Hemminger [this message]
2020-01-02 18:22 ` [PATCH] drivers/net/b44: Change to non-atomic bit operations Luck, Tony
2020-01-03 8:47 ` David Laight
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