Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751400AbdH3Irz (ORCPT ); Wed, 30 Aug 2017 04:47:55 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:39328 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751271AbdH3Irx (ORCPT ); Wed, 30 Aug 2017 04:47:53 -0400 Date: Wed, 30 Aug 2017 10:47:46 +0200 From: Peter Zijlstra To: Sergey Senozhatsky Cc: Byungchul Park , Bart Van Assche , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "martin.petersen@oracle.com" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "sfr@canb.auug.org.au" , "linux-next@vger.kernel.org" , kernel-team@lge.com Subject: Re: possible circular locking dependency detected [was: linux-next: Tree for Aug 22] Message-ID: <20170830084746.GC660@worktop.programming.kicks-ass.net> References: <20170822183816.7925e0f8@canb.auug.org.au> <20170822104708.GA491@jagdpanzerIV.localdomain> <1503438234.2508.27.camel@wdc.com> <20170823000304.GK20323@X58A-UD3R> <20170830052037.GA432@jagdpanzerIV.localdomain> <20170830054334.GF3240@X58A-UD3R> <20170830061511.GA330@jagdpanzerIV.localdomain> <20170830084207.GL32112@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170830084207.GL32112@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 956 Lines: 26 On Wed, Aug 30, 2017 at 10:42:07AM +0200, Peter Zijlstra wrote: > > So the overhead looks to be spread out over all sorts, which makes it > harder to find and fix. > > stack unwinding is done lots and is fairly expensive, I've not yet > checked if crossrelease does too much of that. Aah, we do an unconditional stack unwind for every __lock_acquire() now. It keeps a trace in the xhlocks[]. Does the below cure most of that overhead? diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 44c8d0d17170..7b872036b72e 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4872,7 +4872,7 @@ static void add_xhlock(struct held_lock *hlock) xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES; xhlock->trace.entries = xhlock->trace_entries; xhlock->trace.skip = 3; - save_stack_trace(&xhlock->trace); + /* save_stack_trace(&xhlock->trace); */ } static inline int same_context_xhlock(struct hist_lock *xhlock)