Commit 87c9741a authored by Saurabh Sengar's avatar Saurabh Sengar Committed by Wei Liu
Browse files

Drivers: hv: vmbus: Optimize boot time by concurrent execution of hv_synic_init() 



Currently on a very large system with 1780 CPUs, hv_acpi_init() takes
around 3 seconds to complete. This is because of sequential synic
initialization for each CPU performed by hv_synic_init().

Schedule these tasks parallelly so that each CPU executes hv_synic_init()
in parallel to take full advantage of multiple CPUs.

This solution saves around 2 seconds of boot time on a 1780 CPU system,
which is around 66% improvement in the existing logic.

Signed-off-by: default avatarSaurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: default avatarNuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: default avatarSrivatsa S. Bhat (Microsoft) <srivatsa@csail.mit.edu>
Reviewed-by: default avatarDexuan Cui <decui@microsoft.com>
Link: https://lore.kernel.org/r/1722488136-6223-1-git-send-email-ssengar@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Message-ID: <1722488136-6223-1-git-send-email-ssengar@linux.microsoft.com>
parent 47ac09b9

drivers/hv/vmbus_drv.c

+31 −3
Original line number Diff line number Diff line
@@ -1306,6 +1306,13 @@ static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id) 
	return IRQ_HANDLED;

}



static void vmbus_percpu_work(struct work_struct *work)

{

	unsigned int cpu = smp_processor_id();



	hv_synic_init(cpu);

}



/*

 * vmbus_bus_init -Main vmbus driver initialization routine.

 *
@@ -1316,7 +1323,8 @@ static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id) 
 */

static int vmbus_bus_init(void)

{

	int ret;

	int ret, cpu;

	struct work_struct __percpu *works;



	ret = hv_init();

	if (ret != 0) {
@@ -1355,12 +1363,32 @@ static int vmbus_bus_init(void) 
	if (ret)

		goto err_alloc;



	works = alloc_percpu(struct work_struct);

	if (!works) {

		ret = -ENOMEM;

		goto err_alloc;

	}



	/*

	 * Initialize the per-cpu interrupt state and stimer state.

	 * Then connect to the host.

	 */

	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",

	cpus_read_lock();

	for_each_online_cpu(cpu) {

		struct work_struct *work = per_cpu_ptr(works, cpu);



		INIT_WORK(work, vmbus_percpu_work);

		schedule_work_on(cpu, work);

	}



	for_each_online_cpu(cpu)

		flush_work(per_cpu_ptr(works, cpu));



	/* Register the callbacks for possible CPU online/offline'ing */

	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",

						   hv_synic_init, hv_synic_cleanup);

	cpus_read_unlock();

	free_percpu(works);

	if (ret < 0)

		goto err_alloc;

	hyperv_cpuhp_online = ret;