Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758868Ab2FFWSR (ORCPT ); Wed, 6 Jun 2012 18:18:17 -0400 Received: from relay.ihostexchange.net ([66.46.182.52]:23644 "EHLO relay.ihostexchange.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754168Ab2FFWSQ convert rfc822-to-8bit (ORCPT ); Wed, 6 Jun 2012 18:18:16 -0400 From: "Shai Fultheim (Shai@ScaleMP.com)" To: Peter Zijlstra , "mingo@kernel.org" , "hpa@zytor.com" , "linux-kernel@vger.kernel.org" , "torvalds@linux-foundation.org" , "akpm@linux-foundation.org" , "tglx@linutronix.de" , "ido@wizery.com" CC: "linux-tip-commits@vger.kernel.org" Date: Wed, 6 Jun 2012 18:18:12 -0400 Subject: RE: [tip:x86/mm] x86/pat: Avoid contention on cpa_lock if possible Thread-Topic: [tip:x86/mm] x86/pat: Avoid contention on cpa_lock if possible Thread-Index: Ac1ECTOquSzc4insTfKVBsH9sAtFdwAKF2KQ Message-ID: <9B14D1490DDECA4E974F6B9FC9EBAB317EEFC74FD0@VMBX108.ihostexchange.net> References: <1334873492-31255-1-git-send-email-ido@wizery.com> <1339003443.23343.6.camel@twins> In-Reply-To: <1339003443.23343.6.camel@twins> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 48 Peter Zijlstra [mailto:a.p.zijlstra@chello.nl] wrote > On Wed, 2012-06-06 at 09:18 -0700, tip-bot for Shai Fultheim wrote: > > > [ I absolutely hate these locking patterns ... yet I have no better idea. Maybe the gents on Cc: ... ] > > Signed-off-by: Ingo Molnar > > Oh yuck, this is vile.. > > static struct static_key scale_mp_trainwreck = STATIC_KEY_INIT_FALSE; > > static DEFINE_SPINLOCK(_cpa_lock); > > static inline void cpa_lock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > static inline void cpa_unlock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > And then use cpa_{,un}lock(), and the scale-mp guys can > static_key_slow_inc(&scale_mp_trainwreck). > > [ and yes I hate those jump_label names ... but I'm not wanting > to go through another round of bike-shed painting. ] Looks pretty straight forward to do. We will try this route, as I'm concerned that synthetic CPUID bit will be kind of a global change for a pretty local consideration. Comments? (and we will also fix the other error pointed by Ingo - we are missing an include in this patch) Regards, Shai. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/