From: Willy Tarreau <w@1wt.eu>
To: Rob Herring <robherring2@gmail.com>
Cc: Arnaud Ebalard <arno@natisbad.org>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Florian Fainelli <f.fainelli@gmail.com>,
simon.guinot@sequanux.org, Eric Dumazet <eric.dumazet@gmail.com>,
netdev@vger.kernel.org, edumazet@google.com,
Cong Wang <xiyou.wangcong@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: ARM network performance and dma_mask
Date: Thu, 21 Nov 2013 23:13:10 +0100 [thread overview]
Message-ID: <20131121221310.GG18513@1wt.eu> (raw)
In-Reply-To: <528E82C6.2010106@gmail.com>
On Thu, Nov 21, 2013 at 04:01:42PM -0600, Rob Herring wrote:
> The patch was to fix this issue[1]. It is fixed in the core code because
> dma_mask not being set has been a known issue with DT probing for some
> time. Since most drivers don't seem to care, we've gotten away with it.
> I thought the normal failure mode was drivers failing to probe.
It seems that very few drivers try to set their mask, so probably that
the default value was already OK even though less performant.
> As to why it helps performance, I'm not really sure. Perhaps it is
> causing some bounce buffers to be used.
That's also the thing I have been thinking about, and given this device
only has a 16-bit DDR bus, bounce buffers can make a difference.
> Rob
>
> [1] http://lists.xen.org/archives/html/xen-devel/2013-10/msg00092.html
Thanks for your quick explanation Rob!
Willy
next prev parent reply other threads:[~2013-11-21 22:13 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-10 13:53 [BUG,REGRESSION?] 3.11.6+,3.12: GbE iface rate drops to few KB/s Arnaud Ebalard
2013-11-12 6:48 ` Cong Wang
2013-11-12 7:56 ` Arnaud Ebalard
2013-11-12 8:36 ` Willy Tarreau
2013-11-12 9:14 ` Arnaud Ebalard
2013-11-12 10:01 ` Willy Tarreau
2013-11-12 15:34 ` Arnaud Ebalard
2013-11-13 7:22 ` Willy Tarreau
2013-11-17 14:19 ` Willy Tarreau
2013-11-17 17:41 ` Eric Dumazet
2013-11-19 6:44 ` Arnaud Ebalard
2013-11-19 13:53 ` Eric Dumazet
2013-11-19 17:43 ` Willy Tarreau
2013-11-19 18:31 ` Eric Dumazet
2013-11-19 18:41 ` Willy Tarreau
2013-11-19 23:53 ` Arnaud Ebalard
2013-11-20 0:08 ` Eric Dumazet
2013-11-20 0:35 ` Willy Tarreau
2013-11-20 0:43 ` Eric Dumazet
2013-11-20 0:52 ` Willy Tarreau
2013-11-20 8:50 ` Thomas Petazzoni
2013-11-20 19:11 ` Willy Tarreau
2013-11-20 19:26 ` Arnaud Ebalard
2013-11-20 21:28 ` Arnaud Ebalard
2013-11-20 21:54 ` Willy Tarreau
2013-11-21 0:44 ` Willy Tarreau
2013-11-21 18:38 ` ARM network performance and dma_mask (was: [BUG,REGRESSION?] 3.11.6+,3.12: GbE iface rate drops to few KB/s) Willy Tarreau
2013-11-21 19:04 ` Thomas Petazzoni
2013-11-21 21:51 ` Willy Tarreau
2013-11-21 22:01 ` ARM network performance and dma_mask Rob Herring
2013-11-21 22:13 ` Willy Tarreau [this message]
2013-11-21 21:51 ` [BUG,REGRESSION?] 3.11.6+,3.12: GbE iface rate drops to few KB/s Arnaud Ebalard
2013-11-21 21:52 ` Willy Tarreau
2013-11-21 22:00 ` Eric Dumazet
2013-11-21 22:55 ` Arnaud Ebalard
2013-11-21 23:23 ` Rick Jones
2013-11-20 17:12 ` Willy Tarreau
2013-11-20 17:30 ` Eric Dumazet
2013-11-20 17:38 ` Willy Tarreau
2013-11-20 18:52 ` David Miller
2013-11-20 17:34 ` Willy Tarreau
2013-11-20 17:40 ` Eric Dumazet
2013-11-20 18:15 ` Willy Tarreau
2013-11-20 18:21 ` Eric Dumazet
2013-11-20 18:29 ` Willy Tarreau
2013-11-20 19:22 ` Arnaud Ebalard
2013-11-18 10:09 ` David Laight
2013-11-18 10:52 ` Willy Tarreau
2013-11-18 10:26 ` Thomas Petazzoni
2013-11-18 10:44 ` Simon Guinot
2013-11-18 16:54 ` Stephen Hemminger
2013-11-18 17:13 ` Eric Dumazet
2013-11-18 10:51 ` Willy Tarreau
2013-11-18 17:58 ` Florian Fainelli
2013-11-12 14:39 ` [PATCH] tcp: tsq: restore minimal amount of queueing Eric Dumazet
2013-11-12 15:24 ` Sujith Manoharan
2013-11-13 14:06 ` Eric Dumazet
2013-11-13 14:32 ` [PATCH v2] " Eric Dumazet
2013-11-13 21:18 ` Arnaud Ebalard
2013-11-13 21:59 ` Holger Hoffstaette
2013-11-13 23:40 ` Eric Dumazet
2013-11-13 23:52 ` Holger Hoffstaette
2013-11-17 23:15 ` Francois Romieu
2013-11-18 16:26 ` Holger Hoffstätte
2013-11-18 16:47 ` Eric Dumazet
2013-11-13 22:41 ` Eric Dumazet
2013-11-14 21:26 ` David Miller
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