From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v2 2/4] locking/qspinlock_stat: Track the no MCS node available case Date: Wed, 23 Jan 2019 09:23:40 +0000 Message-ID: <20190123092339.GD15019@brain-police> References: <1548215351-18896-1-git-send-email-longman@redhat.com> <1548215351-18896-3-git-send-email-longman@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1548215351-18896-3-git-send-email-longman@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Waiman Long Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, Zhenzhong Duan , James Morse , SRINIVAS List-Id: linux-arch.vger.kernel.org On Tue, Jan 22, 2019 at 10:49:09PM -0500, Waiman Long wrote: > Track the number of slowpath locking operations that are being done > without any MCS node available as well renaming lock_index[123] to make > them more descriptive. > > Using these stat counters is one way to find out if a code path is > being exercised. > > Signed-off-by: Waiman Long > --- > kernel/locking/qspinlock.c | 3 ++- > kernel/locking/qspinlock_stat.h | 21 +++++++++++++++------ > 2 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c > index 0875053..21ee51b 100644 > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -422,6 +422,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > * simple enough. > */ > if (unlikely(idx >= MAX_NODES)) { > + qstat_inc(qstat_lock_no_node, true); > while (!queued_spin_trylock(lock)) > cpu_relax(); > goto release; > @@ -432,7 +433,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > /* > * Keep counts of non-zero index values: > */ > - qstat_inc(qstat_lock_idx1 + idx - 1, idx); > + qstat_inc(qstat_lock_use_node2 + idx - 1, idx); > > /* > * Ensure that we increment the head node->count before initialising > diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h > index 42d3d8d..31728f6 100644 > --- a/kernel/locking/qspinlock_stat.h > +++ b/kernel/locking/qspinlock_stat.h > @@ -30,6 +30,13 @@ > * pv_wait_node - # of vCPU wait's at a non-head queue node > * lock_pending - # of locking operations via pending code > * lock_slowpath - # of locking operations via MCS lock queue > + * lock_use_node2 - # of locking operations that use 2nd percpu node > + * lock_use_node3 - # of locking operations that use 3rd percpu node > + * lock_use_node4 - # of locking operations that use 4th percpu node > + * lock_no_node - # of locking operations without using percpu node > + * > + * Subtraccting lock_use_node[234] from lock_slowpath will give you > + * lock_use_node1. Typo: "subtraccting" Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:37922 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726326AbfAWJXr (ORCPT ); Wed, 23 Jan 2019 04:23:47 -0500 Date: Wed, 23 Jan 2019 09:23:40 +0000 From: Will Deacon Subject: Re: [PATCH v2 2/4] locking/qspinlock_stat: Track the no MCS node available case Message-ID: <20190123092339.GD15019@brain-police> References: <1548215351-18896-1-git-send-email-longman@redhat.com> <1548215351-18896-3-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1548215351-18896-3-git-send-email-longman@redhat.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Waiman Long Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, Zhenzhong Duan , James Morse , SRINIVAS Message-ID: <20190123092340.lEEW6kg0bquG_QJHO_1Gy44OyKCgx6cRlrPTbckrI2c@z> On Tue, Jan 22, 2019 at 10:49:09PM -0500, Waiman Long wrote: > Track the number of slowpath locking operations that are being done > without any MCS node available as well renaming lock_index[123] to make > them more descriptive. > > Using these stat counters is one way to find out if a code path is > being exercised. > > Signed-off-by: Waiman Long > --- > kernel/locking/qspinlock.c | 3 ++- > kernel/locking/qspinlock_stat.h | 21 +++++++++++++++------ > 2 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c > index 0875053..21ee51b 100644 > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -422,6 +422,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > * simple enough. > */ > if (unlikely(idx >= MAX_NODES)) { > + qstat_inc(qstat_lock_no_node, true); > while (!queued_spin_trylock(lock)) > cpu_relax(); > goto release; > @@ -432,7 +433,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) > /* > * Keep counts of non-zero index values: > */ > - qstat_inc(qstat_lock_idx1 + idx - 1, idx); > + qstat_inc(qstat_lock_use_node2 + idx - 1, idx); > > /* > * Ensure that we increment the head node->count before initialising > diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h > index 42d3d8d..31728f6 100644 > --- a/kernel/locking/qspinlock_stat.h > +++ b/kernel/locking/qspinlock_stat.h > @@ -30,6 +30,13 @@ > * pv_wait_node - # of vCPU wait's at a non-head queue node > * lock_pending - # of locking operations via pending code > * lock_slowpath - # of locking operations via MCS lock queue > + * lock_use_node2 - # of locking operations that use 2nd percpu node > + * lock_use_node3 - # of locking operations that use 3rd percpu node > + * lock_use_node4 - # of locking operations that use 4th percpu node > + * lock_no_node - # of locking operations without using percpu node > + * > + * Subtraccting lock_use_node[234] from lock_slowpath will give you > + * lock_use_node1. Typo: "subtraccting" Will