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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 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191015_213221_084583_252A63FD X-CRM114-Status: GOOD ( 24.01 ) X-Spam-Score: -2.5 (--) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-2.5 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [156.151.31.85 listed in list.dnswl.org] -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.0 UNPARSEABLE_RELAY Informational: message has unparseable relay lines -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alex.kogan@oracle.com, dave.dice@oracle.com, rahul.x.yadav@oracle.com, steven.sistare@oracle.com, daniel.m.jordan@oracle.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.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);