From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D296DC4360C for ; Wed, 16 Oct 2019 04:32:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5B84217D6 for ; Wed, 16 Oct 2019 04:32:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="hPw37+d8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390743AbfJPEcw (ORCPT ); Wed, 16 Oct 2019 00:32:52 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:33534 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390491AbfJPEcs (ORCPT ); Wed, 16 Oct 2019 00:32:48 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x9G4SZUS166019; Wed, 16 Oct 2019 04:31:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=corp-2019-08-05; bh=nwli1ZwecEZzyJZyU9LI7xjeU0hbh0ChVjhSfnDI9y8=; b=hPw37+d8AUUGAbIpgXQ1KErxr79V7RZ0r/ZJGX1VDHEqmimB7cYBh3BuTuoe5SFAsgIM qOpD7Q83domlfvcFgbgK25TkxIjUw5drjeQ7eucGJKn5Nr+VVB6E9tovh+WyoQpqL2nh qdXTR6ZjU6yFyW0xHa109cQMfPypafj7CL6VDiqd5Upv8gHkV82SuXvkIEW2eqJt0uhu ErojsBMDPx4YQT1x3BF3oyfC1y+bjWYw+JRHk0s+p9J2ZXwSONX3ILleHuRXJ3jGgr9b Ia8n9QOb+wki5R7NR34SEqn56+bYSYZenIEMcbXO/O4JiBYgqgP4s04ynvaL96QOF088 Kw== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2120.oracle.com with ESMTP id 2vk7frbxgv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 16 Oct 2019 04:31:24 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x9G4RfS5042717; Wed, 16 Oct 2019 04:31:24 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 2vn8epsv7a-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 16 Oct 2019 04:31:24 +0000 Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x9G4VB8N028634; Wed, 16 Oct 2019 04:31:11 GMT Received: from neelam.us.oracle.com (/10.152.128.16) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 15 Oct 2019 21:31:11 -0700 From: Alex Kogan To: linux@armlinux.org.uk, peterz@infradead.org, mingo@redhat.com, will.deacon@arm.com, arnd@arndb.de, longman@redhat.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de, hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com, jglauber@marvell.com Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, alex.kogan@oracle.com, dave.dice@oracle.com, rahul.x.yadav@oracle.com Subject: [PATCH v5 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Date: Wed, 16 Oct 2019 00:29:02 -0400 Message-Id: <20191016042903.61081-5-alex.kogan@oracle.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20191016042903.61081-1-alex.kogan@oracle.com> References: <20191016042903.61081-1-alex.kogan@oracle.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9411 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910160040 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9411 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910160040 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Keep track of the number of intra-node lock handoffs, and force inter-node handoff once this number reaches a preset threshold. Signed-off-by: Alex Kogan Reviewed-by: Steve Sistare --- kernel/locking/qspinlock.c | 3 +++ kernel/locking/qspinlock_cna.h | 30 +++++++++++++++++++++++++++--- 2 files changed, 30 insertions(+), 3 deletions(-) diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 6d8c4a52e44e..1d0d884308ef 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -597,6 +597,9 @@ EXPORT_SYMBOL(queued_spin_lock_slowpath); #if !defined(_GEN_CNA_LOCK_SLOWPATH) && defined(CONFIG_NUMA_AWARE_SPINLOCKS) #define _GEN_CNA_LOCK_SLOWPATH +#undef pv_init_node +#define pv_init_node cna_init_node + #undef pv_wait_head_or_lock #define pv_wait_head_or_lock cna_pre_scan diff --git a/kernel/locking/qspinlock_cna.h b/kernel/locking/qspinlock_cna.h index 4d095f742d31..b92a6f9a19db 100644 --- a/kernel/locking/qspinlock_cna.h +++ b/kernel/locking/qspinlock_cna.h @@ -50,9 +50,19 @@ struct cna_node { struct mcs_spinlock mcs; int numa_node; u32 encoded_tail; - u32 pre_scan_result; /* 0 or an encoded tail */ + u32 pre_scan_result; /* 0, 1 or an encoded tail */ + u32 intra_count; }; +/* + * Controls the threshold for the number of intra-node lock hand-offs. It can + * be tuned and depend, e.g., on the number of CPUs per node. For now, + * choose a value that provides reasonable long-term fairness without + * sacrificing performance compared to a version that does not have any + * fairness guarantees. + */ +#define INTRA_NODE_HANDOFF_THRESHOLD (1 << 16) + static void __init cna_init_nodes_per_cpu(unsigned int cpu) { struct mcs_spinlock *base = per_cpu_ptr(&qnodes[0].mcs, cpu); @@ -86,6 +96,11 @@ static void __init cna_init_nodes(void) } early_initcall(cna_init_nodes); +static __always_inline void cna_init_node(struct mcs_spinlock *node) +{ + ((struct cna_node *)node)->intra_count = 0; +} + static inline bool cna_try_change_tail(struct qspinlock *lock, u32 val, struct mcs_spinlock *node) { @@ -215,7 +230,13 @@ __always_inline u32 cna_pre_scan(struct qspinlock *lock, { struct cna_node *cn = (struct cna_node *)node; - cn->pre_scan_result = cna_scan_main_queue(node, node); + /* + * setting @pre_scan_result to 1 indicates that no post-scan + * should be made in cna_pass_lock() + */ + cn->pre_scan_result = + cn->intra_count == INTRA_NODE_HANDOFF_THRESHOLD ? + 1 : cna_scan_main_queue(node, node); return 0; } @@ -234,7 +255,7 @@ static inline void cna_pass_lock(struct mcs_spinlock *node, * pre-scan, and if so, try to find it in post-scan starting from the * node where pre-scan stopped (stored in @pre_scan_result) */ - if (scan > 0) + if (scan > 1) scan = cna_scan_main_queue(node, decode_tail(scan)); if (!scan) { /* if found a successor from the same numa node */ @@ -245,6 +266,9 @@ static inline void cna_pass_lock(struct mcs_spinlock *node, * to pass the lock */ val = node->locked + (node->locked == 0); + /* inc @intra_count if the secondary queue is not empty */ + ((struct cna_node *)next_holder)->intra_count = + cn->intra_count + (node->locked > 1); } else if (node->locked > 1) { /* if secondary queue is not empty */ /* next holder will be the first node in the secondary queue */ tail_2nd = decode_tail(node->locked); -- 2.11.0 (Apple Git-81)