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Fri, 14 May 2021 13:07:59 -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 Subject: [PATCH v15 5/6] locking/qspinlock: Avoid moving certain threads between waiting queues in CNA Date: Fri, 14 May 2021 16:07:42 -0400 Message-Id: <20210514200743.3026725-6-alex.kogan@oracle.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210514200743.3026725-1-alex.kogan@oracle.com> References: <20210514200743.3026725-1-alex.kogan@oracle.com> MIME-Version: 1.0 X-Proofpoint-GUID: xuu9t5RUNNTjssDrPPvistR2qAfhAMQO X-Proofpoint-ORIG-GUID: xuu9t5RUNNTjssDrPPvistR2qAfhAMQO X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9984 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 bulkscore=0 adultscore=0 priorityscore=1501 phishscore=0 malwarescore=0 spamscore=0 impostorscore=0 mlxlogscore=999 mlxscore=0 clxscore=1011 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105140159 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210514_130902_956985_4AADF325 X-CRM114-Status: GOOD ( 23.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Prohibit moving certain threads (e.g., in irq and nmi contexts) to the secondary queue. Those prioritized threads will always stay in the primary queue, and so will have a shorter wait time for the lock. Signed-off-by: Alex Kogan Reviewed-by: Steve Sistare Reviewed-by: Waiman Long --- kernel/locking/qspinlock_cna.h | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/kernel/locking/qspinlock_cna.h b/kernel/locking/qspinlock_cna.h index 0b991c340fb1..ffc5c3301f0f 100644 --- a/kernel/locking/qspinlock_cna.h +++ b/kernel/locking/qspinlock_cna.h @@ -6,6 +6,7 @@ #include #include #include +#include /* * Implement a NUMA-aware version of MCS (aka CNA, or compact NUMA-aware lock). @@ -37,7 +38,8 @@ * running on the same NUMA node. If it is not, that waiter is detached from the * main queue and moved into the tail of the secondary queue. This way, we * gradually filter the primary queue, leaving only waiters running on the same - * preferred NUMA node. + * preferred NUMA node. Note that certain priortized waiters (e.g., in + * irq and nmi contexts) are excluded from being moved to the secondary queue. * * We change the NUMA node preference after a waiter at the head of the * secondary queue spins for a certain amount of time (1ms, by default). @@ -53,6 +55,8 @@ #define FLUSH_SECONDARY_QUEUE 1 +#define CNA_PRIORITY_NODE 0xffff + struct cna_node { struct mcs_spinlock mcs; u16 numa_node; @@ -111,9 +115,10 @@ static int __init cna_init_nodes(void) static __always_inline void cna_init_node(struct mcs_spinlock *node) { + bool priority = !in_task() || irqs_disabled() || rt_task(current); struct cna_node *cn = (struct cna_node *)node; - cn->numa_node = cn->real_numa_node; + cn->numa_node = priority ? CNA_PRIORITY_NODE : cn->real_numa_node; cn->start_time = 0; } @@ -252,7 +257,7 @@ static int cna_order_queue(struct mcs_spinlock *node) numa_node = cn->numa_node; next_numa_node = ((struct cna_node *)next)->numa_node; - if (next_numa_node != numa_node) { + if (next_numa_node != numa_node && next_numa_node != CNA_PRIORITY_NODE) { struct mcs_spinlock *nnext = READ_ONCE(next->next); if (nnext) @@ -272,6 +277,13 @@ static __always_inline u32 cna_wait_head_or_lock(struct qspinlock *lock, struct cna_node *cn = (struct cna_node *)node; if (!cn->start_time || !intra_node_threshold_reached(cn)) { + /* + * We are at the head of the wait queue, no need to use + * the fake NUMA node ID. + */ + if (cn->numa_node == CNA_PRIORITY_NODE) + cn->numa_node = cn->real_numa_node; + /* * Try and put the time otherwise spent spin waiting on * _Q_LOCKED_PENDING_MASK to use by sorting our lists. -- 2.24.3 (Apple Git-128) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel