From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Eric Van Hensbergen <ericvh@gmail.com>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
bg-linux@lists.anl-external.org
Subject: Re: [PATCH 5/7] [RFC] force 32-byte aligned kmallocs
Date: Fri, 20 May 2011 11:50:03 +1000 [thread overview]
Message-ID: <1305856203.7481.116.camel@pasglop> (raw)
In-Reply-To: <BANLkTimc3jQTOJdqAiqbPxGQNVWe39VqfQ@mail.gmail.com>
On Thu, 2011-05-19 at 19:47 -0500, Eric Van Hensbergen wrote:
> On Thu, May 19, 2011 at 7:36 PM, Benjamin Herrenschmidt
> <benh@kernel.crashing.org> wrote:
> > On Wed, 2011-05-18 at 16:24 -0500, Eric Van Hensbergen wrote:
> >>
> >> -#ifdef CONFIG_NOT_COHERENT_CACHE
> >> +#if defined(CONFIG_NOT_COHERENT_CACHE) || defined(CONFIG_BGP)
> >> #define ARCH_DMA_MINALIGN L1_CACHE_BYTES
> >> #endif
> >
> > Is DMA cache coherent on BG/P ? That's odd for a 4xx base :-)
> >
>
> My understanding of things (which could be totally wrong) is that the
> DMA we care about on BG/P (namely the Torus and Collective networks)
> is coherent at the L2. Of course the change in question is talking
> about L1_CACHE_BYTES, so my reading of this is that its a sleazy way
> of getting aligned mallocs that make interactions with the tightly
> coupled networks easier/more-efficient. I'm open to alternative
> suggestions.
But if it's not coherent with L1, then you sould have
CONFIG_NOT_COHERENT_CACHE set and not need that patch... or am I missing
something ?
One thing we should do some day as well is make that whole non-coherent
be runtime selected, on the list of things to fix 440+47x in the same
kernel. Pfiew....
Cheers,
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Eric Van Hensbergen <ericvh@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
bg-linux@lists.anl-external.org
Subject: Re: [PATCH 5/7] [RFC] force 32-byte aligned kmallocs
Date: Fri, 20 May 2011 11:50:03 +1000 [thread overview]
Message-ID: <1305856203.7481.116.camel@pasglop> (raw)
In-Reply-To: <BANLkTimc3jQTOJdqAiqbPxGQNVWe39VqfQ@mail.gmail.com>
On Thu, 2011-05-19 at 19:47 -0500, Eric Van Hensbergen wrote:
> On Thu, May 19, 2011 at 7:36 PM, Benjamin Herrenschmidt
> <benh@kernel.crashing.org> wrote:
> > On Wed, 2011-05-18 at 16:24 -0500, Eric Van Hensbergen wrote:
> >>
> >> -#ifdef CONFIG_NOT_COHERENT_CACHE
> >> +#if defined(CONFIG_NOT_COHERENT_CACHE) || defined(CONFIG_BGP)
> >> #define ARCH_DMA_MINALIGN L1_CACHE_BYTES
> >> #endif
> >
> > Is DMA cache coherent on BG/P ? That's odd for a 4xx base :-)
> >
>
> My understanding of things (which could be totally wrong) is that the
> DMA we care about on BG/P (namely the Torus and Collective networks)
> is coherent at the L2. Of course the change in question is talking
> about L1_CACHE_BYTES, so my reading of this is that its a sleazy way
> of getting aligned mallocs that make interactions with the tightly
> coupled networks easier/more-efficient. I'm open to alternative
> suggestions.
But if it's not coherent with L1, then you sould have
CONFIG_NOT_COHERENT_CACHE set and not need that patch... or am I missing
something ?
One thing we should do some day as well is make that whole non-coherent
be runtime selected, on the list of things to fix 440+47x in the same
kernel. Pfiew....
Cheers,
Ben.
next prev parent reply other threads:[~2011-05-20 1:50 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-18 21:24 [PATCH 1/7] [RFC] Mainline BG/P platform support Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-18 21:24 ` [PATCH 2/7] [RFC] add bluegene entry to cputable Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-20 0:35 ` Benjamin Herrenschmidt
2011-05-20 0:35 ` Benjamin Herrenschmidt
2011-05-20 1:08 ` Eric Van Hensbergen
2011-05-20 1:08 ` Eric Van Hensbergen
2011-05-20 1:50 ` Benjamin Herrenschmidt
2011-05-20 1:50 ` Benjamin Herrenschmidt
2011-05-18 21:24 ` [PATCH 3/7] [RFC] add support for BlueGene/P FPU Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-19 5:58 ` Michael Neuling
2011-05-19 5:58 ` Michael Neuling
2011-05-19 13:53 ` Eric Van Hensbergen
2011-05-19 13:53 ` Eric Van Hensbergen
2011-05-19 15:22 ` [bg-linux] " Kazutomo Yoshii
2011-05-19 21:36 ` Michael Neuling
2011-05-19 21:36 ` Michael Neuling
2011-05-19 21:55 ` Eric Van Hensbergen
2011-05-19 21:55 ` Eric Van Hensbergen
2011-05-19 23:16 ` Michael Neuling
2011-05-19 23:16 ` Michael Neuling
2011-05-20 0:30 ` Eric Van Hensbergen
2011-05-20 0:30 ` Eric Van Hensbergen
2011-05-20 0:43 ` Michael Neuling
2011-05-20 0:43 ` Michael Neuling
2011-05-20 0:53 ` Benjamin Herrenschmidt
2011-05-20 0:52 ` Benjamin Herrenschmidt
2011-05-20 0:52 ` Benjamin Herrenschmidt
2011-05-19 21:41 ` [PATCH 3/7] [RFC][V2] add support for BlueGene/P Double FPU Eric Van Hensbergen
2011-05-19 21:41 ` Eric Van Hensbergen
2011-05-18 21:24 ` [PATCH 4/7] [RFC] enable L1_WRITETHROUGH mode for BG/P Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-19 10:43 ` Josh Boyer
2011-05-19 10:43 ` Josh Boyer
2011-05-19 12:53 ` Eric Van Hensbergen
2011-05-19 12:53 ` Eric Van Hensbergen
2011-05-19 21:42 ` [PATCH 4/7] [RFC][V2] enable BGP_L1_WRITETHROUGH " Eric Van Hensbergen
2011-05-19 21:42 ` Eric Van Hensbergen
2011-05-20 1:01 ` [PATCH 4/7] [RFC] enable L1_WRITETHROUGH " Benjamin Herrenschmidt
2011-05-20 1:01 ` Benjamin Herrenschmidt
2011-05-18 21:24 ` [PATCH 5/7] [RFC] force 32-byte aligned kmallocs Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-20 0:36 ` Benjamin Herrenschmidt
2011-05-20 0:36 ` Benjamin Herrenschmidt
2011-05-20 0:47 ` Eric Van Hensbergen
2011-05-20 0:47 ` Eric Van Hensbergen
2011-05-20 1:50 ` Benjamin Herrenschmidt [this message]
2011-05-20 1:50 ` Benjamin Herrenschmidt
2011-05-20 1:32 ` [bg-linux] " Kazutomo Yoshii
2011-05-20 2:08 ` Benjamin Herrenschmidt
2011-05-20 2:08 ` Benjamin Herrenschmidt
2011-05-20 2:13 ` Benjamin Herrenschmidt
2011-05-20 2:13 ` Benjamin Herrenschmidt
2011-05-20 3:02 ` Kazutomo Yoshii
2011-05-20 3:13 ` Benjamin Herrenschmidt
2011-05-18 21:24 ` [PATCH 6/7] [RFC] enable early TLBs for BG/P Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-20 0:39 ` Benjamin Herrenschmidt
2011-05-20 0:39 ` Benjamin Herrenschmidt
2011-05-20 1:21 ` Eric Van Hensbergen
2011-05-20 1:21 ` Eric Van Hensbergen
2011-05-20 1:54 ` Benjamin Herrenschmidt
2011-05-20 1:54 ` Benjamin Herrenschmidt
2011-05-20 3:38 ` [bg-linux] " Kazutomo Yoshii
2011-05-20 3:38 ` Kazutomo Yoshii
2011-05-20 3:52 ` Benjamin Herrenschmidt
2011-05-20 3:52 ` Benjamin Herrenschmidt
2011-05-20 13:01 ` Eric Van Hensbergen
2011-05-20 22:20 ` Benjamin Herrenschmidt
2011-05-18 21:24 ` [PATCH 7/7] [RFC] SMP support code Eric Van Hensbergen
2011-05-18 21:24 ` Eric Van Hensbergen
2011-05-20 1:05 ` Benjamin Herrenschmidt
2011-05-20 1:05 ` Benjamin Herrenschmidt
2011-05-19 11:01 ` [PATCH 1/7] [RFC] Mainline BG/P platform support Josh Boyer
2011-05-19 11:01 ` Josh Boyer
2011-05-19 12:35 ` Eric Van Hensbergen
2011-05-19 12:35 ` Eric Van Hensbergen
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