scsi: megaraid_sas: Added support for shared host tagset for cpuhotplug

Fusion adapters can steer completions to individual queues, and
we now have support for shared host-wide tags.
So we can enable multiqueue support for fusion adapters.

Once driver enable shared host-wide tags, cpu hotplug feature is also
supported as it was enabled using below patchsets -
commit bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are
offline")

Currently driver has provision to disable host-wide tags using
"host_tagset_enable" module parameter.

Once we do not have any major performance regression using host-wide
tags, we will drop the hand-crafted interrupt affinity settings.

Performance is also meeting the expecatation - (used both none and
mq-deadline scheduler)
24 Drive SSD on Aero with/without this patch can get 3.1M IOPs
3 VDs consist of 8 SAS SSD on Aero with/without this patch can get 3.1M
IOPs.

Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
index 2b7e7b5f38ed..020270ce790b 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -37,6 +37,7 @@
 #include <linux/poll.h>
 #include <linux/vmalloc.h>
 #include <linux/irq_poll.h>
+#include <linux/blk-mq-pci.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -113,6 +114,10 @@ unsigned int enable_sdev_max_qd;
 module_param(enable_sdev_max_qd, int, 0444);
 MODULE_PARM_DESC(enable_sdev_max_qd, "Enable sdev max qd as can_queue. Default: 0");
 
+int host_tagset_enable = 1;
+module_param(host_tagset_enable, int, 0444);
+MODULE_PARM_DESC(host_tagset_enable, "Shared host tagset enable/disable Default: enable(1)");
+
 MODULE_LICENSE("GPL");
 MODULE_VERSION(MEGASAS_VERSION);
 MODULE_AUTHOR("megaraidlinux.pdl@broadcom.com");
@@ -3119,6 +3124,19 @@ megasas_bios_param(struct scsi_device *sdev, struct block_device *bdev,
 	return 0;
 }
 
+static int megasas_map_queues(struct Scsi_Host *shost)
+{
+	struct megasas_instance *instance;
+
+	instance = (struct megasas_instance *)shost->hostdata;
+
+	if (shost->nr_hw_queues == 1)
+		return 0;
+
+	return blk_mq_pci_map_queues(&shost->tag_set.map[HCTX_TYPE_DEFAULT],
+			instance->pdev, instance->low_latency_index_start);
+}
+
 static void megasas_aen_polling(struct work_struct *work);
 
 /**
@@ -3427,6 +3445,7 @@ static struct scsi_host_template megasas_template = {
 	.eh_timed_out = megasas_reset_timer,
 	.shost_attrs = megaraid_host_attrs,
 	.bios_param = megasas_bios_param,
+	.map_queues = megasas_map_queues,
 	.change_queue_depth = scsi_change_queue_depth,
 	.max_segment_size = 0xffffffff,
 };
@@ -6808,6 +6827,26 @@ static int megasas_io_attach(struct megasas_instance *instance)
 	host->max_lun = MEGASAS_MAX_LUN;
 	host->max_cmd_len = 16;
 
+	/* Use shared host tagset only for fusion adaptors
+	 * if there are managed interrupts (smp affinity enabled case).
+	 * Single msix_vectors in kdump, so shared host tag is also disabled.
+	 */
+
+	host->host_tagset = 0;
+	host->nr_hw_queues = 1;
+
+	if ((instance->adapter_type != MFI_SERIES) &&
+		(instance->msix_vectors > instance->low_latency_index_start) &&
+		host_tagset_enable &&
+		instance->smp_affinity_enable) {
+		host->host_tagset = 1;
+		host->nr_hw_queues = instance->msix_vectors -
+			instance->low_latency_index_start;
+	}
+
+	dev_info(&instance->pdev->dev,
+		"Max firmware commands: %d shared with nr_hw_queues = %d\n",
+		instance->max_fw_cmds, host->nr_hw_queues);
 	/*
 	 * Notify the mid-layer about the new controller
 	 */