From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc Date: Sat, 23 Apr 2016 18:25:49 +1000 Message-ID: <1461399949.3135.52.camel@kernel.crashing.org> References: <1461139097-10213-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1461278876.3135.18.camel@kernel.crashing.org> <20160422160927.GB12897@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20160422160927.GB12897@obsidianresearch.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: "Linuxppc-dev" To: Jason Gunthorpe Cc: linux-rdma@vger.kernel.org, Mike Marciniszyn , Doug Ledford , paulus@samba.org, "Aneesh Kumar K.V" , Sean Hefty , linuxppc-dev@lists.ozlabs.org, Hal Rosenstock List-Id: linux-rdma@vger.kernel.org T24gRnJpLCAyMDE2LTA0LTIyIGF0IDEwOjA5IC0wNjAwLCBKYXNvbiBHdW50aG9ycGUgd3JvdGU6 Cj4gT24gRnJpLCBBcHIgMjIsIDIwMTYgYXQgMDg6NDc6NTZBTSArMTAwMCwgQmVuamFtaW4gSGVy cmVuc2NobWlkdAo+IHdyb3RlOgo+ID4gCj4gPiBPbiBXZWQsIDIwMTYtMDQtMjAgYXQgMDM6NTgg LTA0MDAsIEFuZWVzaCBLdW1hciBLLlYgd3JvdGU6Cj4gPiA+IAo+ID4gPiBUaGUgZHJpdmVyIHdh cyByZXF1ZXN0aW5nIGZvciBhIHdyaXRldGhyb3VnaCBtYXBwaW5nLiBCdXQgd2l0aAo+ID4gPiB0 aG9zZXMKPiA+ID4gZmxhZ3Mgd2Ugd2lsbCBlbmQgdXAgd2l0aCBhIFNBTyBtYXBwaW5nIGJlY2F1 c2Ugd2Ugbm93IGhhdmUKPiA+ID4gbWVtb3J5Cj4gPiA+IGNvbmhlcmVuY2UgYWx3YXlzIGVuYWJs ZWQuIGllLCB0aGUgZXhpc3RpbmcgbWFwcGluZyB3aWxsIGVuZCB1cAo+ID4gPiB3aXRoCj4gPiA+ IGEgV0lNRyB2YWx1ZSAwYjExMTAgd2hpY2ggaXMgU3Ryb25nIEFjY2VzcyBPcmRlci4KPiA+ID4g Cj4gPiA+IFVwZGF0ZSB0aGlzIHRvIHVzZSBjYWNoZSBpbmhpYml0dGVkIGd1YXJkZWQgbWFwcGlu Zwo+ID4gV2h5IGd1YXJkZWQgPyBJZiBpdCdzIHBlcmZvcm1hbmNlIHNlbnNpdGl2ZSAoYW5kIHRo ZSBkcml2ZXIgaGFzCj4gPiBhcHByb3ByaWF0ZSBiYXJyaWVycyB3aGVyZSBuZWVkZWQpLCB5b3Ug d2lsbCBnZXQgd3JpdGUgY29tYmluaW5nCj4gPiB3aXRob3V0IGd1YXJkZWQsIHlvdSB3b24ndCB3 aXRoIGl0Lgo+IFRoaXMgZHJpdmVyIHVzZXMgdW5jYWNoZWQgd3JpdGUgY29tYmluaW5nIG9uIHg4 NgoKUmlnaHQgc28gaWYgeW91IHdhbnQgc29tZXRoaW5nIHNpbWlsYXIgb24gcG93ZXIsIHVzZSB0 aGUgX3djIHZhcmlhbnQsCmFuZCBtYWtlIHN1cmUgeW91IGhhdmUgdGhlIGFwcHJvcHJpYXRlIGJh cnJpZXJzIHdoZW4geW91IG5lZWQgdG8KYnJlYWsgY29tYmluaW5nLgoKQ2hlZXJzLApCZW4uCgpf X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpMaW51eHBwYy1k ZXYgbWFpbGluZyBsaXN0CkxpbnV4cHBjLWRldkBsaXN0cy5vemxhYnMub3JnCmh0dHBzOi8vbGlz dHMub3psYWJzLm9yZy9saXN0aW5mby9saW51eHBwYy1kZXY= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qsQYk474pzDq60 for ; Sat, 23 Apr 2016 18:26:18 +1000 (AEST) Message-ID: <1461399949.3135.52.camel@kernel.crashing.org> Subject: Re: [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc From: Benjamin Herrenschmidt To: Jason Gunthorpe Cc: "Aneesh Kumar K.V" , paulus@samba.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, Mike Marciniszyn , Doug Ledford , Sean Hefty , Hal Rosenstock , linux-rdma@vger.kernel.org Date: Sat, 23 Apr 2016 18:25:49 +1000 In-Reply-To: <20160422160927.GB12897@obsidianresearch.com> References: <1461139097-10213-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1461278876.3135.18.camel@kernel.crashing.org> <20160422160927.GB12897@obsidianresearch.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.