From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish() Date: Wed, 20 Feb 2019 14:47:05 +0000 Message-ID: <20190220144705.GH7523@fuggles.cambridge.arm.com> References: <20190219103148.192029670@infradead.org> <20190219103233.207580251@infradead.org> <20190219124738.GD8501@fuggles.cambridge.arm.com> <20190219134147.GZ32494@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190219134147.GZ32494@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org To: Peter Zijlstra Cc: aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, npiggin@gmail.com, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux@armlinux.org.uk, heiko.carstens@de.ibm.com, riel@surriel.com, tony.luck@intel.com List-Id: linux-arch.vger.kernel.org On Tue, Feb 19, 2019 at 02:41:47PM +0100, Peter Zijlstra wrote: > On Tue, Feb 19, 2019 at 12:47:38PM +0000, Will Deacon wrote: > > Fine for now, but I agree that we should drop the hook altogether. AFAICT, > > this only exists to help an ia64 optimisation which looks suspicious to > > me since it uses: > > > > mm == current->active_mm && atomic_read(&mm->mm_users) == 1 > > > > to identify a "single-threaded fork()" and therefore perform only local TLB > > invalidation. Even if this was the right thing to do, it's not clear to me > > that tlb_migrate_finish() is called on the right CPU anyway. > > > > So I'd be keen to remove this hook before it spreads, but in the meantime: > > Agreed :-) > > The obvious slash and kill patch ... untested I'm also unable to test this, unfortunately. Can we get it into next after the merge window and see if anybody reports issues? Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:59130 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727177AbfBTOrK (ORCPT ); Wed, 20 Feb 2019 09:47:10 -0500 Date: Wed, 20 Feb 2019 14:47:05 +0000 From: Will Deacon Subject: Re: [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish() Message-ID: <20190220144705.GH7523@fuggles.cambridge.arm.com> References: <20190219103148.192029670@infradead.org> <20190219103233.207580251@infradead.org> <20190219124738.GD8501@fuggles.cambridge.arm.com> <20190219134147.GZ32494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190219134147.GZ32494@hirez.programming.kicks-ass.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, npiggin@gmail.com, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux@armlinux.org.uk, heiko.carstens@de.ibm.com, riel@surriel.com, tony.luck@intel.com Message-ID: <20190220144705.rCFJQWI5PjwaiMqazGoFYc8oybg4LwbMJmmhD1YsHJY@z> On Tue, Feb 19, 2019 at 02:41:47PM +0100, Peter Zijlstra wrote: > On Tue, Feb 19, 2019 at 12:47:38PM +0000, Will Deacon wrote: > > Fine for now, but I agree that we should drop the hook altogether. AFAICT, > > this only exists to help an ia64 optimisation which looks suspicious to > > me since it uses: > > > > mm == current->active_mm && atomic_read(&mm->mm_users) == 1 > > > > to identify a "single-threaded fork()" and therefore perform only local TLB > > invalidation. Even if this was the right thing to do, it's not clear to me > > that tlb_migrate_finish() is called on the right CPU anyway. > > > > So I'd be keen to remove this hook before it spreads, but in the meantime: > > Agreed :-) > > The obvious slash and kill patch ... untested I'm also unable to test this, unfortunately. Can we get it into next after the merge window and see if anybody reports issues? Will