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Mon, 25 Nov 2019 21:17:23 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xAPL8RMV041281; Mon, 25 Nov 2019 21:15:22 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2wfewb4m0y-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 25 Nov 2019 21:15:22 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id xAPLFHbH027504; Mon, 25 Nov 2019 21:15:17 GMT Received: from neelam.us.oracle.com (/10.152.128.16) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 25 Nov 2019 13:15:16 -0800 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 v7 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Date: Mon, 25 Nov 2019 16:07:08 -0500 Message-Id: <20191125210709.10293-5-alex.kogan@oracle.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20191125210709.10293-1-alex.kogan@oracle.com> References: <20191125210709.10293-1-alex.kogan@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9452 signatures=668685 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=8.0.1-1911140001 definitions=main-1911250171 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9452 signatures=668685 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=8.0.1-1911140001 definitions=main-1911250171 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191125_131749_839416_DC10250A X-CRM114-Status: GOOD ( 25.52 ) 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 [141.146.126.78 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's 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. The default value for the threshold can be overridden with the new kernel boot command-line option "numa_spinlock_threshold". Signed-off-by: Alex Kogan Reviewed-by: Steve Sistare --- .../admin-guide/kernel-parameters.txt | 8 ++++++ arch/x86/kernel/alternative.c | 27 +++++++++++++++++++ kernel/locking/qspinlock.c | 3 +++ kernel/locking/qspinlock_cna.h | 27 ++++++++++++++++--- 4 files changed, 62 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 904cb32f592d..887fbfce701d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3185,6 +3185,14 @@ Not specifying this option is equivalent to numa_spinlock=auto. + numa_spinlock_threshold= [NUMA, PV_OPS] + Set the threshold for the number of intra-node + lock hand-offs before the NUMA-aware spinlock + is forced to be passed to a thread on another NUMA node. + Valid values are in the [0..31] range. Smaller values + result in a more fair, but less performant spinlock, and + vice versa. The default value is 16. + cpu0_hotplug [X86] Turn on CPU0 hotplug feature when CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. Some features depend on CPU0. Known dependencies are: diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 6a4ccbf4e09c..28552e0491b5 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -723,6 +723,33 @@ static int __init numa_spinlock_setup(char *str) __setup("numa_spinlock=", numa_spinlock_setup); +/* + * Controls the threshold for the number of intra-node lock hand-offs before + * the NUMA-aware variant of spinlock is forced to be passed to a thread on + * another NUMA node. By default, the chosen value provides reasonable + * long-term fairness without sacrificing performance compared to a lock + * that does not have any fairness guarantees. + */ +int intra_node_handoff_threshold = 1 << 16; + +static int __init numa_spinlock_threshold_setup(char *str) +{ + int new_threshold_param; + + if (get_option(&str, &new_threshold_param)) { + /* valid value is between 0 and 31 */ + if (new_threshold_param < 0 || new_threshold_param > 31) + return 0; + + intra_node_handoff_threshold = 1 << new_threshold_param; + return 1; + } + + return 0; +} + +__setup("numa_spinlock_threshold=", numa_spinlock_threshold_setup); + #endif void __init alternative_instructions(void) 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 a638336f9560..dcb2bcfd2d94 100644 --- a/kernel/locking/qspinlock_cna.h +++ b/kernel/locking/qspinlock_cna.h @@ -50,9 +50,16 @@ struct cna_node { struct mcs_spinlock mcs; int numa_node; u32 encoded_tail; - u32 pre_scan_result; /* 0 or encoded tail */ + u32 pre_scan_result; /* 0, 1 or encoded tail */ + u32 intra_count; }; +/* + * Controls the threshold for the number of intra-node lock hand-offs. + * See arch/x86/kernel/alternative.c for details. + */ +extern int intra_node_handoff_threshold; + static void __init cna_init_nodes_per_cpu(unsigned int cpu) { struct mcs_spinlock *base = per_cpu_ptr(&qnodes[0].mcs, cpu); @@ -92,6 +99,11 @@ static int __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) { @@ -221,7 +233,13 @@ __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; } @@ -240,7 +258,7 @@ 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 */ @@ -251,6 +269,9 @@ static inline void cna_pass_lock(struct mcs_spinlock *node, * if we acquired the MCS lock when its queue was empty */ val = node->locked ? node->locked : 1; + /* 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);