On Fri, Aug 2, 2019 at 6:09 AM James Smart <jsmart2021@xxxxxxxxx> wrote:
>
> 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
I guess the numa node number is 4 in your test machine. Per my observation,
the performance is often very close if the hw queue count is set as numa node
number.
> 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@xxxxxxxxxxxx>
> Signed-off-by: James Smart <jsmart2021@xxxxxxxxx>
> CC: Ming Lei <tom.leiming@xxxxxxxxx>
>
> ---
> v2:
> revised to set nr_hw_queues to minimum of 2 per numa node or
> max value specified by module parameter.
> raised default value for module parameter to 8.
> ---
> drivers/scsi/lpfc/lpfc.h | 1 +
> drivers/scsi/lpfc/lpfc_attr.c | 15 +++++++++++++++
> drivers/scsi/lpfc/lpfc_init.c | 10 ++++++----
> drivers/scsi/lpfc/lpfc_sli4.h | 5 +++++
> 4 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/lpfc/lpfc.h b/drivers/scsi/lpfc/lpfc.h
> index 2c3bb8a966e5..bade2e025ecf 100644
> --- 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 ea62322ffe2b..8d8c495b5b60 100644
> --- a/drivers/scsi/lpfc/lpfc_attr.c
> +++ b/drivers/scsi/lpfc/lpfc_attr.c
> @@ -5709,6 +5709,19 @@ 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
> * will map to the number of CQ/WQ pairs the driver will create.
> @@ -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 faf43b1d3dbe..03998579d6ee 100644
> --- 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);
Hi James,
I am wondering why you use 2 * num_possible_nodes() as the limit instead of
num_possible_nodes(), could you explain it a bit?
Thanks,
Ming Lei
