From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751485AbcFCEfY (ORCPT ); Fri, 3 Jun 2016 00:35:24 -0400 Received: from gate.crashing.org ([63.228.1.57]:38005 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750829AbcFCEfX (ORCPT ); Fri, 3 Jun 2016 00:35:23 -0400 Message-ID: <1464928427.26773.26.camel@kernel.crashing.org> Subject: Re: [PATCH v5 1/6] qspinlock: powerpc support qspinlock From: Benjamin Herrenschmidt To: xinhui , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org Cc: paulus@samba.org, mpe@ellerman.id.au, peterz@infradead.org, mingo@redhat.com, paulmck@linux.vnet.ibm.com, waiman.long@hpe.com Date: Fri, 03 Jun 2016 14:33:47 +1000 In-Reply-To: <57510353.1020209@linux.vnet.ibm.com> References: <1464859370-5162-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1464859370-5162-3-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1464917520.26773.11.camel@kernel.crashing.org> <1464917548.26773.12.camel@au1.ibm.com> <57510353.1020209@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2 (3.18.5.2-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2016-06-03 at 12:10 +0800, xinhui wrote: > On 2016年06月03日 09:32, Benjamin Herrenschmidt wrote: > > On Fri, 2016-06-03 at 11:32 +1000, Benjamin Herrenschmidt wrote: > >> On Thu, 2016-06-02 at 17:22 +0800, Pan Xinhui wrote: > >>> > >>> Base code to enable qspinlock on powerpc. this patch add some > >>> #ifdef > >>> here and there. Although there is no paravirt related code, we > can > >>> successfully build a qspinlock kernel after apply this patch. > >> This is missing the IO_SYNC stuff ... It means we'll fail to do a > >> full > >> sync to order vs MMIOs. > >> > >> You need to add that back in the unlock path. > > > > Well, and in the lock path as well... > > > Oh, yes. I missed IO_SYNC stuff. > > thank you, Ben :) Ok couple of other things that would be nice from my perspective (and Michael's) if you can produce them:  - Some benchmarks of the qspinlock alone, without the PV stuff,    so we understand how much of the overhead is inherent to the    qspinlock and how much is introduced by the PV bits.  - For the above, can you show (or describe) where the qspinlock    improves things compared to our current locks. While there's    theory and to some extent practice on x86, it would be nice to    validate the effects on POWER.  - Comparative benchmark with the PV stuff in on a bare metal system    to understand the overhead there.  - Comparative benchmark with the PV stuff under pHyp and KVM Spinlocks are fiddly and a critical piece of infrastructure, it's important we fully understand the performance implications before we decide to switch to a new model. Cheers, Ben. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH v5 1/6] qspinlock: powerpc support qspinlock Date: Fri, 03 Jun 2016 14:33:47 +1000 Message-ID: <1464928427.26773.26.camel@kernel.crashing.org> References: <1464859370-5162-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1464859370-5162-3-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1464917520.26773.11.camel@kernel.crashing.org> <1464917548.26773.12.camel@au1.ibm.com> <57510353.1020209@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <57510353.1020209@linux.vnet.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: xinhui , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org Cc: peterz@infradead.org, mpe@ellerman.id.au, waiman.long@hpe.com, mingo@redhat.com, paulus@samba.org, paulmck@linux.vnet.ibm.com List-Id: virtualization@lists.linuxfoundation.org T24gRnJpLCAyMDE2LTA2LTAzIGF0IDEyOjEwICswODAwLCB4aW5odWkgd3JvdGU6Cj4gT24gMjAx NuW5tDA25pyIMDPml6UgMDk6MzIsIEJlbmphbWluIEhlcnJlbnNjaG1pZHQgd3JvdGU6Cj4gPiBP biBGcmksIDIwMTYtMDYtMDMgYXQgMTE6MzIgKzEwMDAsIEJlbmphbWluIEhlcnJlbnNjaG1pZHQg d3JvdGU6Cj4gPj4gT24gVGh1LCAyMDE2LTA2LTAyIGF0IDE3OjIyICswODAwLCBQYW4gWGluaHVp IHdyb3RlOgo+ID4+Pgo+ID4+PiBCYXNlIGNvZGUgdG8gZW5hYmxlIHFzcGlubG9jayBvbiBwb3dl cnBjLiB0aGlzIHBhdGNoIGFkZCBzb21lCj4gPj4+ICNpZmRlZgo+ID4+PiBoZXJlIGFuZCB0aGVy ZS4gQWx0aG91Z2ggdGhlcmUgaXMgbm8gcGFyYXZpcnQgcmVsYXRlZCBjb2RlLCB3ZQo+IGNhbgo+ ID4+PiBzdWNjZXNzZnVsbHkgYnVpbGQgYSBxc3BpbmxvY2sga2VybmVsIGFmdGVyIGFwcGx5IHRo aXMgcGF0Y2guCj4gPj4gVGhpcyBpcyBtaXNzaW5nIHRoZSBJT19TWU5DIHN0dWZmIC4uLiBJdCBt ZWFucyB3ZSdsbCBmYWlsIHRvIGRvIGEKPiA+PiBmdWxsCj4gPj4gc3luYyB0byBvcmRlciB2cyBN TUlPcy4KPiA+Pgo+ID4+IFlvdSBuZWVkIHRvIGFkZCB0aGF0IGJhY2sgaW4gdGhlIHVubG9jayBw YXRoLgo+ID4KPiA+IFdlbGwsIGFuZCBpbiB0aGUgbG9jayBwYXRoIGFzIHdlbGwuLi4KPiA+Cj4g T2gsIHllcy4gSSBtaXNzZWQgSU9fU1lOQyBzdHVmZi4KPiAKPiB0aGFuayB5b3UsIEJlbiA6KQoK T2sgY291cGxlIG9mIG90aGVyIHRoaW5ncyB0aGF0IHdvdWxkIGJlIG5pY2UgZnJvbSBteSBwZXJz cGVjdGl2ZSAoYW5kCk1pY2hhZWwncykgaWYgeW91IGNhbiBwcm9kdWNlIHRoZW06CgrCoC0gU29t ZSBiZW5jaG1hcmtzIG9mIHRoZSBxc3BpbmxvY2sgYWxvbmUsIHdpdGhvdXQgdGhlIFBWIHN0dWZm LArCoCDCoHNvIHdlIHVuZGVyc3RhbmQgaG93IG11Y2ggb2YgdGhlIG92ZXJoZWFkIGlzIGluaGVy ZW50IHRvIHRoZQrCoCDCoHFzcGlubG9jayBhbmQgaG93IG11Y2ggaXMgaW50cm9kdWNlZCBieSB0 aGUgUFYgYml0cy4KCsKgLSBGb3IgdGhlIGFib3ZlLCBjYW4geW91IHNob3cgKG9yIGRlc2NyaWJl KSB3aGVyZSB0aGUgcXNwaW5sb2NrCsKgIMKgaW1wcm92ZXMgdGhpbmdzIGNvbXBhcmVkIHRvIG91 ciBjdXJyZW50IGxvY2tzLiBXaGlsZSB0aGVyZSdzCsKgIMKgdGhlb3J5IGFuZCB0byBzb21lIGV4 dGVudCBwcmFjdGljZSBvbiB4ODYsIGl0IHdvdWxkIGJlIG5pY2UgdG8KwqAgwqB2YWxpZGF0ZSB0 aGUgZWZmZWN0cyBvbiBQT1dFUi4KCsKgLSBDb21wYXJhdGl2ZSBiZW5jaG1hcmsgd2l0aCB0aGUg UFYgc3R1ZmYgaW4gb24gYSBiYXJlIG1ldGFsIHN5c3RlbQrCoCDCoHRvIHVuZGVyc3RhbmQgdGhl IG92ZXJoZWFkIHRoZXJlLgoKwqAtIENvbXBhcmF0aXZlIGJlbmNobWFyayB3aXRoIHRoZSBQViBz dHVmZiB1bmRlciBwSHlwIGFuZCBLVk0KClNwaW5sb2NrcyBhcmUgZmlkZGx5IGFuZCBhIGNyaXRp Y2FsIHBpZWNlIG9mIGluZnJhc3RydWN0dXJlLCBpdCdzCmltcG9ydGFudCB3ZSBmdWxseSB1bmRl cnN0YW5kIHRoZSBwZXJmb3JtYW5jZSBpbXBsaWNhdGlvbnMgYmVmb3JlIHdlCmRlY2lkZSB0byBz d2l0Y2ggdG8gYSBuZXcgbW9kZWwuCgpDaGVlcnMsCkJlbi4KCl9fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fClZpcnR1YWxpemF0aW9uIG1haWxpbmcgbGlzdApW aXJ0dWFsaXphdGlvbkBsaXN0cy5saW51eC1mb3VuZGF0aW9uLm9yZwpodHRwczovL2xpc3RzLmxp bnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby92aXJ0dWFsaXphdGlvbg==