From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: linux-rdma@vger.kernel.org,
Mike Marciniszyn <infinipath@intel.com>,
Doug Ledford <dledford@redhat.com>,
paulus@samba.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Sean Hefty <sean.hefty@intel.com>,
linuxppc-dev@lists.ozlabs.org,
Hal Rosenstock <hal.rosenstock@gmail.com>
Subject: Re: [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc
Date: Sat, 23 Apr 2016 18:25:49 +1000 [thread overview]
Message-ID: <1461399949.3135.52.camel@kernel.crashing.org> (raw)
In-Reply-To: <20160422160927.GB12897@obsidianresearch.com>
On Fri, 2016-04-22 at 10:09 -0600, Jason Gunthorpe wrote:
> On Fri, Apr 22, 2016 at 08:47:56AM +1000, Benjamin Herrenschmidt
> wrote:
> >
> > On Wed, 2016-04-20 at 03:58 -0400, Aneesh Kumar K.V wrote:
> > >
> > > The driver was requesting for a writethrough mapping. But with
> > > thoses
> > > flags we will end up with a SAO mapping because we now have
> > > memory
> > > conherence always enabled. ie, the existing mapping will end up
> > > with
> > > a WIMG value 0b1110 which is Strong Access Order.
> > >
> > > Update this to use cache inhibitted guarded mapping
> > Why guarded ? If it's performance sensitive (and the driver has
> > appropriate barriers where needed), you will get write combining
> > without guarded, you won't with it.
> This driver uses uncached write combining on x86
Right so if you want something similar on power, use the _wc variant,
and make sure you have the appropriate barriers when you need to
break combining.
Cheers,
Ben.
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Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
paulus@samba.org, mpe@ellerman.id.au,
linuxppc-dev@lists.ozlabs.org,
Mike Marciniszyn <infinipath@intel.com>,
Doug Ledford <dledford@redhat.com>,
Sean Hefty <sean.hefty@intel.com>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
linux-rdma@vger.kernel.org
Subject: Re: [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc
Date: Sat, 23 Apr 2016 18:25:49 +1000 [thread overview]
Message-ID: <1461399949.3135.52.camel@kernel.crashing.org> (raw)
In-Reply-To: <20160422160927.GB12897@obsidianresearch.com>
On Fri, 2016-04-22 at 10:09 -0600, Jason Gunthorpe wrote:
> On Fri, Apr 22, 2016 at 08:47:56AM +1000, Benjamin Herrenschmidt
> wrote:
> >
> > On Wed, 2016-04-20 at 03:58 -0400, Aneesh Kumar K.V wrote:
> > >
> > > The driver was requesting for a writethrough mapping. But with
> > > thoses
> > > flags we will end up with a SAO mapping because we now have
> > > memory
> > > conherence always enabled. ie, the existing mapping will end up
> > > with
> > > a WIMG value 0b1110 which is Strong Access Order.
> > >
> > > Update this to use cache inhibitted guarded mapping
> > Why guarded ? If it's performance sensitive (and the driver has
> > appropriate barriers where needed), you will get write combining
> > without guarded, you won't with it.
> This driver uses uncached write combining on x86
Right so if you want something similar on power, use the _wc variant,
and make sure you have the appropriate barriers when you need to
break combining.
Cheers,
Ben.
next prev parent reply other threads:[~2016-04-23 8:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-20 7:58 [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc Aneesh Kumar K.V
2016-04-20 7:58 ` Aneesh Kumar K.V
2016-04-20 16:29 ` Marciniszyn, Mike
2016-04-20 16:29 ` Marciniszyn, Mike
[not found] ` <32E1700B9017364D9B60AED9960492BC25ACE29D-RjuIdWtd+YbTXloPLtfHfbfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2016-04-26 11:03 ` Michael Ellerman
2016-04-26 11:03 ` Michael Ellerman
2016-04-21 22:47 ` Benjamin Herrenschmidt
2016-04-21 22:47 ` Benjamin Herrenschmidt
[not found] ` <1461278876.3135.18.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2016-04-22 16:09 ` Jason Gunthorpe
2016-04-22 16:09 ` Jason Gunthorpe
2016-04-23 8:25 ` Benjamin Herrenschmidt [this message]
2016-04-23 8:25 ` Benjamin Herrenschmidt
[not found] ` <1461399949.3135.52.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2016-04-24 17:33 ` Aneesh Kumar K.V
2016-04-24 17:33 ` Aneesh Kumar K.V
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