From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com>,
Tom Herbert <therbert@google.com>,
Denys Fedoryshchenko <denys@visp.net.lb>,
netdev@vger.kernel.org, e1000-devel@lists.sourceforge.net,
jeffrey.t.kirsher@intel.com, jesse.brandeburg@intel.com,
davem@davemloft.net
Subject: RE: Strange latency spikes/TX network stalls on Sun Fire X4150(x86) and e1000e
Date: Wed, 30 May 2012 13:04:55 +0200 [thread overview]
Message-ID: <1338375895.2760.153.camel@edumazet-glaptop> (raw)
In-Reply-To: <AE90C24D6B3A694183C094C60CF0A2F6026B6F31@saturn3.aculab.com>
On Wed, 2012-05-30 at 11:52 +0100, David Laight wrote:
> > > + num_queued = dql->num_queued;
> >
> >
> > I suggest :
> >
> > num_queued = ACCESS_ONCE(dql->num_queued);
> >
> > Or else compiler is free to do whatever he wants.
>
> Or make the structure member volatile, then the
> compiler can only read it once.
No. Compiler can read it several times. Really.
> Probably worth while if the value is expected to
> be read like that.
Please don't use lazy volatile.
Unless you really want Linus flames (and ours)
ACCESS_ONCE() is much cleaner.
next prev parent reply other threads:[~2012-05-30 11:05 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-15 14:15 Strange latency spikes/TX network stalls on Sun Fire X4150(x86) and e1000e Denys Fedoryshchenko
2012-05-17 13:42 ` Denys Fedoryshchenko
2012-05-17 16:54 ` Denys Fedoryshchenko
2012-05-18 14:04 ` Denys Fedoryshchenko
2012-05-19 2:07 ` Tom Herbert
2012-05-19 2:29 ` Denys Fedoryshchenko
2012-05-19 2:40 ` Denys Fedoryshchenko
2012-05-20 17:40 ` Tom Herbert
2012-05-20 18:53 ` Denys Fedoryshchenko
2012-05-20 19:07 ` Eric Dumazet
2012-05-20 19:18 ` Denys Fedoryshchenko
2012-05-21 3:56 ` Eric Dumazet
2012-05-21 8:06 ` Denys Fedoryshchenko
2012-05-21 8:30 ` Eric Dumazet
2012-05-21 8:40 ` Eric Dumazet
2012-05-21 9:22 ` Denys Fedoryshchenko
2012-05-22 17:11 ` Denys Fedoryshchenko
2012-05-22 17:24 ` Eric Dumazet
2012-05-25 6:01 ` Tom Herbert
2012-05-25 6:22 ` Eric Dumazet
2012-05-25 16:59 ` Tom Herbert
2012-05-25 17:18 ` Eric Dumazet
2012-05-29 14:25 ` Hiroaki SHIMODA
2012-05-29 14:54 ` Tom Herbert
2012-05-29 15:11 ` Eric Dumazet
2012-05-29 19:52 ` Denys Fedoryshchenko
2012-05-30 0:06 ` Hiroaki SHIMODA
2012-05-30 8:40 ` Eric Dumazet
2012-05-30 10:43 ` Hiroaki SHIMODA
2012-05-30 11:08 ` Eric Dumazet
2012-05-30 11:20 ` Joe Perches
2012-05-30 11:59 ` Eric Dumazet
2012-05-30 14:09 ` Joe Perches
2012-05-30 14:42 ` Eric Dumazet
2012-05-30 14:50 ` Joe Perches
2012-05-30 11:29 ` Hiroaki SHIMODA
2012-05-30 14:49 ` Eric Dumazet
2012-05-30 15:00 ` dave taht
2012-05-30 22:19 ` Hiroaki SHIMODA
2012-05-30 10:52 ` David Laight
2012-05-30 11:04 ` Eric Dumazet [this message]
2012-05-30 11:12 ` Eric Dumazet
2012-06-06 5:10 ` Eric Dumazet
2012-06-06 8:43 ` Hiroaki SHIMODA
2012-06-06 16:26 ` Jesse Brandeburg
2012-06-06 17:05 ` Eric Dumazet
2012-06-06 17:26 ` David Miller
2012-06-06 17:19 ` Hiroaki SHIMODA
2012-06-06 18:21 ` Tom Herbert
2012-06-06 18:23 ` David Miller
2012-06-06 18:46 ` Stephen Hemminger
2012-05-20 18:13 ` Eric Dumazet
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