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[2620:137:e000::1:20]) by mx.google.com with ESMTP id q18-20020a17090311d200b001867a6a1791si377263plh.426.2022.10.24.12.30.37; Mon, 24 Oct 2022 12:30:52 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b="DWzb+n/5"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230311AbiJXT1e (ORCPT + 99 others); Mon, 24 Oct 2022 15:27:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230055AbiJXT0U (ORCPT ); Mon, 24 Oct 2022 15:26:20 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 886FC72FD3 for ; Mon, 24 Oct 2022 10:58:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666634295; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fCvbSgxKkVngETIOIh3AmCdsye2c6FCNzZDR+LWaBok=; b=DWzb+n/5GMSSkudDS0cgxtdghZ6VmYC/AVHqZjS9RN+4es+Dv2mxBbqQKywUCBnPGnOJOJ 41axuWjq/DUM3wWt0Aca0l354BS+ctwtV/708WVBYg0+HyKY77i0d/Cig2q0E2KqQO5zAr WvWK1zyQVS/yj4QTkakUt11yKN8YiRo= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-137-lPIKskdWP3-rNMpu5I5t0w-1; Mon, 24 Oct 2022 13:44:52 -0400 X-MC-Unique: lPIKskdWP3-rNMpu5I5t0w-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D49A63817960; Mon, 24 Oct 2022 17:44:51 +0000 (UTC) Received: from llong.com (dhcp-17-153.bos.redhat.com [10.18.17.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8F12C492B0E; Mon, 24 Oct 2022 17:44:51 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng Cc: linux-kernel@vger.kernel.org, john.p.donnelly@oracle.com, Hillf Danton , Mukesh Ojha , =?utf-8?b?VGluZzExIFdhbmcg546L5am3?= , Waiman Long Subject: [PATCH v4 5/5] locking/rwsem: Update handoff lock events tracking Date: Mon, 24 Oct 2022 13:44:18 -0400 Message-Id: <20221024174418.796468-6-longman@redhat.com> In-Reply-To: <20221024174418.796468-1-longman@redhat.com> References: <20221024174418.796468-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747598549651492681?= X-GMAIL-MSGID: =?utf-8?q?1747598549651492681?= With the new direct rwsem lock handoff, the corresponding handoff lock events are updated to also track the number of secondary lock handoffs in rwsem_down_read_slowpath() to see how prevalent those handoff events are. The number of primary lock handoffs in the unlock paths is (rwsem_handoff_read + rwsem_handoff_write - rwsem_handoff_rslow). After running a 96-thread rwsem microbenchmark with equal number of readers and writers on a 2-socket 96-thread system for 40s, the following handoff stats were obtained: rwsem_handoff_read=189 rwsem_handoff_rslow=1 rwsem_handoff_write=6678 rwsem_handoff_wspin=6681 The number of primary handoffs was 6866, whereas there was only one secondary handoff for this test run. Signed-off-by: Waiman Long --- kernel/locking/lock_events_list.h | 6 ++++-- kernel/locking/rwsem.c | 9 +++++---- 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/locking/lock_events_list.h b/kernel/locking/lock_events_list.h index 97fb6f3f840a..04d101767c2c 100644 --- a/kernel/locking/lock_events_list.h +++ b/kernel/locking/lock_events_list.h @@ -63,7 +63,9 @@ LOCK_EVENT(rwsem_rlock) /* # of read locks acquired */ LOCK_EVENT(rwsem_rlock_steal) /* # of read locks by lock stealing */ LOCK_EVENT(rwsem_rlock_fast) /* # of fast read locks acquired */ LOCK_EVENT(rwsem_rlock_fail) /* # of failed read lock acquisitions */ -LOCK_EVENT(rwsem_rlock_handoff) /* # of read lock handoffs */ LOCK_EVENT(rwsem_wlock) /* # of write locks acquired */ LOCK_EVENT(rwsem_wlock_fail) /* # of failed write lock acquisitions */ -LOCK_EVENT(rwsem_wlock_handoff) /* # of write lock handoffs */ +LOCK_EVENT(rwsem_handoff_read) /* # of read lock handoffs */ +LOCK_EVENT(rwsem_handoff_write) /* # of write lock handoffs */ +LOCK_EVENT(rwsem_handoff_rslow) /* # of handoffs in read slowpath */ +LOCK_EVENT(rwsem_handoff_wspin) /* # of handoff spins in write slowpath */ diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 287606aee0e6..46aea1994bf8 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -472,10 +472,8 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, * force the issue. */ if (time_after(jiffies, waiter->timeout)) { - if (!(oldcount & RWSEM_FLAG_HANDOFF)) { + if (!(oldcount & RWSEM_FLAG_HANDOFF)) adjustment -= RWSEM_FLAG_HANDOFF; - lockevent_inc(rwsem_rlock_handoff); - } WRITE_ONCE(waiter->handoff_state, HANDOFF_REQUESTED); } @@ -680,7 +678,6 @@ static inline bool rwsem_try_write_lock(struct rw_semaphore *sem, */ if (new & RWSEM_FLAG_HANDOFF) { WRITE_ONCE(first->handoff_state, HANDOFF_REQUESTED); - lockevent_inc(rwsem_wlock_handoff); return false; } @@ -1019,10 +1016,12 @@ static void rwsem_handoff(struct rw_semaphore *sem, long adj, wake_type = RWSEM_WAKE_ANY; adj += RWSEM_WRITER_LOCKED; atomic_long_set(&sem->owner, (long)waiter->task); + lockevent_inc(rwsem_handoff_write); } else { wake_type = RWSEM_WAKE_READ_OWNED; adj += RWSEM_READER_BIAS; __rwsem_set_reader_owned(sem, waiter->task); + lockevent_inc(rwsem_handoff_read); } atomic_long_add(adj, &sem->count); rwsem_mark_wake(sem, wake_type, wake_q); @@ -1128,6 +1127,7 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat if (rwsem_first_waiter(sem)->type == RWSEM_WAITING_FOR_READ) adjustment = 0; rwsem_handoff(sem, adjustment, &wake_q); + lockevent_inc(rwsem_handoff_rslow); if (!adjustment) { raw_spin_unlock_irq(&sem->wait_lock); @@ -1257,6 +1257,7 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state) preempt_disable(); rwsem_spin_on_owner(sem); preempt_enable(); + lockevent_inc(rwsem_handoff_wspin); } if (READ_ONCE(waiter.handoff_state) == HANDOFF_GRANTED) goto skip_sleep;