Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763391AbZFQH7V (ORCPT ); Wed, 17 Jun 2009 03:59:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754272AbZFQH7N (ORCPT ); Wed, 17 Jun 2009 03:59:13 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:41681 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753916AbZFQH7M (ORCPT ); Wed, 17 Jun 2009 03:59:12 -0400 Subject: Re: [tip:perfcounters/core] x86: Add NMI types for kmap_atomic From: Peter Zijlstra To: Hugh Dickins Cc: Ingo Molnar , linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, paulus@samba.org, acme@redhat.com, efault@gmx.de, npiggin@suse.de, tglx@linutronix.de, linux-tip-commits@vger.kernel.org, Linus Torvalds , Andrew Morton , Tejun Heo In-Reply-To: References: <1245080486.6800.561.camel@laptop> <1245089065.13761.19316.camel@twins> <20090615181555.GA11248@elte.hu> <1245089943.13761.19334.camel@twins> <20090615182549.GD11248@elte.hu> <1245090608.13761.19349.camel@twins> <20090615184217.GG11248@elte.hu> <1245091674.6741.180.camel@laptop> <20090615185259.GK11248@elte.hu> <1245092433.6741.201.camel@laptop> <20090616081348.GC16229@elte.hu> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 17 Jun 2009 09:58:38 +0200 Message-Id: <1245225518.13761.21617.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1010 Lines: 22 On Tue, 2009-06-16 at 13:38 +0100, Hugh Dickins wrote: > > Something else to throw in: what if they were not just atomic, > but also replaced the current sleeping kmaps? i.e. a task context > carries around its own stack of these. I actually did that once, but it means the task needs to be cpu-affine, because fixmaps have different addresses between cpus. And disabling migration for tasks has subtle side-effects so I dropped that again. However, I recently considered the possiblity of putting the fixmaps in the new per-cpu address space so that we might use the %gs segment to normalize the fixmap addresses between the cpus. This would allow full preemptible kmaps (yay for -rt). However I suspect it might greatly complicate kmaps for the !i386 world. -- 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/