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: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/lpfc/lpfc.h b/drivers/scsi/lpfc/lpfc.h
index 2c3bb8a966e5af1cc88412c2eb74a3e527d7a03f..bade2e025ecf2c73b2fdf0869d2e0f8652877c0e 100644 (file)
--- a/drivers/scsi/lpfc/lpfc.h
+++ b/drivers/scsi/lpfc/lpfc.h
@@ -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;

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index ea62322ffe2bb7e711bc87d521903573550be282..8d8c495b5b60c87506526aeee498435b9950273b 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -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);

diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
index a7549ae32542738cce6a8c4011911f1462ff09d1..1ac98becb5baf6b64516c47c267a958bee462e77 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_init.c
+++ b/drivers/scsi/lpfc/lpfc_init.c
@@ -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;

diff --git a/drivers/scsi/lpfc/lpfc_sli4.h b/drivers/scsi/lpfc/lpfc_sli4.h
index 3aeca387b22a4d3a253403e269652bb3bf108c94..329f7aa7e169bb2e62d431360f799bab7f0d0b7f 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_sli4.h
+++ b/drivers/scsi/lpfc/lpfc_sli4.h
@@ -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