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Commit 77ffd346 authored by James Smart's avatar James Smart Committed by Martin K. Petersen
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scsi: lpfc: Mitigate high memory pre-allocation by SCSI-MQ 



When SCSI-MQ is enabled, the SCSI-MQ layers will do pre-allocation of MQ
resources based on shost values set by the driver. In newer cases of the
driver, which attempts to set nr_hw_queues to the cpu count, the
multipliers become excessive, with a single shost having SCSI-MQ
pre-allocation reaching into the multiple GBytes range.  NPIV, which
creates additional shosts, only multiply this overhead. On lower-memory
systems, this can exhaust system memory very quickly, resulting in a system
crash or failures in the driver or elsewhere due to low memory conditions.

After testing several scenarios, the situation can be mitigated by limiting
the value set in shost->nr_hw_queues to 4. Although the shost values were
changed, the driver still had per-cpu hardware queues of its own that
allowed parallelization per-cpu.  Testing revealed that even with the
smallish number for nr_hw_queues for SCSI-MQ, performance levels remained
near maximum with the within-driver affiinitization.

A module parameter was created to allow the value set for the nr_hw_queues
to be tunable.

Signed-off-by: default avatarDick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: default avatarJames Smart <jsmart2021@gmail.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarEwan D. Milne <emilne@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 7c7cfdcf

drivers/scsi/lpfc/lpfc.h

+1 −0
Original line number Diff line number Diff line
@@ -824,6 +824,7 @@ struct lpfc_hba { 
	uint32_t cfg_cq_poll_threshold;

	uint32_t cfg_cq_max_proc_limit;

	uint32_t cfg_fcp_cpu_map;

	uint32_t cfg_fcp_mq_threshold;

	uint32_t cfg_hdw_queue;

	uint32_t cfg_irq_chann;

	uint32_t cfg_suppress_rsp;

drivers/scsi/lpfc/lpfc_attr.c

+15 −0
Original line number Diff line number Diff line
@@ -5708,6 +5708,19 @@ LPFC_ATTR_RW(nvme_oas, 0, 0, 1, 
LPFC_ATTR_RW(nvme_embed_cmd, 1, 0, 2,

	     "Embed NVME Command in WQE");



/*

 * lpfc_fcp_mq_threshold: Set the maximum number of Hardware Queues

 * the driver will advertise it supports to the SCSI layer.

 *

 *      0    = Set nr_hw_queues by the number of CPUs or HW queues.

 *      1,128 = Manually specify the maximum nr_hw_queue value to be set,

 *

 * Value range is [0,128]. Default value is 8.

 */

LPFC_ATTR_R(fcp_mq_threshold, LPFC_FCP_MQ_THRESHOLD_DEF,

	    LPFC_FCP_MQ_THRESHOLD_MIN, LPFC_FCP_MQ_THRESHOLD_MAX,

	    "Set the number of SCSI Queues advertised");



/*

 * lpfc_hdw_queue: Set the number of Hardware Queues the driver

 * will advertise it supports to the NVME and  SCSI layers. This also
@@ -6030,6 +6043,7 @@ struct device_attribute *lpfc_hba_attrs[] = { 
	&dev_attr_lpfc_cq_poll_threshold,

	&dev_attr_lpfc_cq_max_proc_limit,

	&dev_attr_lpfc_fcp_cpu_map,

	&dev_attr_lpfc_fcp_mq_threshold,

	&dev_attr_lpfc_hdw_queue,

	&dev_attr_lpfc_irq_chann,

	&dev_attr_lpfc_suppress_rsp,
@@ -7112,6 +7126,7 @@ lpfc_get_cfgparam(struct lpfc_hba *phba) 
	/* Initialize first burst. Target vs Initiator are different. */

	lpfc_nvme_enable_fb_init(phba, lpfc_nvme_enable_fb);

	lpfc_nvmet_fb_size_init(phba, lpfc_nvmet_fb_size);

	lpfc_fcp_mq_threshold_init(phba, lpfc_fcp_mq_threshold);

	lpfc_hdw_queue_init(phba, lpfc_hdw_queue);

	lpfc_irq_chann_init(phba, lpfc_irq_chann);

	lpfc_enable_bbcr_init(phba, lpfc_enable_bbcr);

drivers/scsi/lpfc/lpfc_init.c

+6 −4
Original line number Diff line number Diff line
@@ -4309,10 +4309,12 @@ lpfc_create_port(struct lpfc_hba *phba, int instance, struct device *dev) 
	shost->max_cmd_len = 16;



	if (phba->sli_rev == LPFC_SLI_REV4) {

		if (phba->cfg_fcp_io_sched == LPFC_FCP_SCHED_BY_HDWQ)

			shost->nr_hw_queues = phba->cfg_hdw_queue;

		else

			shost->nr_hw_queues = phba->sli4_hba.num_present_cpu;

		if (!phba->cfg_fcp_mq_threshold ||

		    phba->cfg_fcp_mq_threshold > phba->cfg_hdw_queue)

			phba->cfg_fcp_mq_threshold = phba->cfg_hdw_queue;



		shost->nr_hw_queues = min_t(int, 2 * num_possible_nodes(),

					    phba->cfg_fcp_mq_threshold);



		shost->dma_boundary =

			phba->sli4_hba.pc_sli4_params.sge_supp_len-1;

drivers/scsi/lpfc/lpfc_sli4.h

+5 −0
Original line number Diff line number Diff line
@@ -44,6 +44,11 @@ 
#define LPFC_HBA_HDWQ_MAX	128

#define LPFC_HBA_HDWQ_DEF	0



/* FCP MQ queue count limiting */

#define LPFC_FCP_MQ_THRESHOLD_MIN	0

#define LPFC_FCP_MQ_THRESHOLD_MAX	128

#define LPFC_FCP_MQ_THRESHOLD_DEF	8



/* Common buffer size to accomidate SCSI and NVME IO buffers */

#define LPFC_COMMON_IO_BUF_SZ	768