Re: [PATCH 1/1] IB/isert: add module param to set sg_tablesize for IO cmd

[Sagi Grimberg <sagi@grimberg.me>]

On 10/11/20 2:06 AM, Max Gurtovoy wrote:
> From: Max Gurtovoy <maxg@mellanox.com>
> 
> Currently, iser target support max IO size of 16MiB by default. For some
> adapters, allocating this amount of resources might reduce the total
> number of possible connections that can be created. For those adapters,
> it's preferred to reduce the max IO size to be able to create more
> connections. Since there is no handshake procedure for max IO size in
> iser protocol, set the default max IO size to 1MiB and add a module
> parameter for enabling the option to control it for suitable adapters.
> 
> Reported-by: Krishnamraju Eraparaju <krishna2@chelsio.com>
> Signed-off-by: Max Gurtovoy <maxg@mellanox.com>

You can add a "Fixes:" tag to help it get to stable.

> ---
>   drivers/infiniband/ulp/isert/ib_isert.c | 27 ++++++++++++++++++++++++-
>   drivers/infiniband/ulp/isert/ib_isert.h |  6 ++++++
>   2 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
> index 695f701dc43d..5a47f1bbca96 100644
> --- a/drivers/infiniband/ulp/isert/ib_isert.c
> +++ b/drivers/infiniband/ulp/isert/ib_isert.c
> @@ -28,6 +28,18 @@ static int isert_debug_level;
>   module_param_named(debug_level, isert_debug_level, int, 0644);
>   MODULE_PARM_DESC(debug_level, "Enable debug tracing if > 0 (default:0)");
>   
> +static int isert_sg_tablesize_set(const char *val,
> +				  const struct kernel_param *kp);
> +static const struct kernel_param_ops sg_tablesize_ops = {
> +	.set = isert_sg_tablesize_set,
> +	.get = param_get_int,
> +};
> +
> +static int isert_sg_tablesize = ISCSI_ISER_SG_TABLESIZE;
> +module_param_cb(sg_tablesize, &sg_tablesize_ops, &isert_sg_tablesize, 0644);
> +MODULE_PARM_DESC(sg_tablesize,
> +		 "Number of gather/scatter entries in a single scsi command, should >= 128 (default: 256, max: 4096)");
> +
>   static DEFINE_MUTEX(device_list_mutex);
>   static LIST_HEAD(device_list);
>   static struct workqueue_struct *isert_comp_wq;
> @@ -47,6 +59,19 @@ static void isert_send_done(struct ib_cq *cq, struct ib_wc *wc);
>   static void isert_login_recv_done(struct ib_cq *cq, struct ib_wc *wc);
>   static void isert_login_send_done(struct ib_cq *cq, struct ib_wc *wc);
>   
> +static int isert_sg_tablesize_set(const char *val, const struct kernel_param *kp)
> +{
> +	int n = 0, ret;
> +
> +	ret = kstrtoint(val, 10, &n);
> +	if (ret != 0 || n < ISCSI_ISER_MIN_SG_TABLESIZE ||
> +	    n > ISCSI_ISER_MAX_SG_TABLESIZE)
> +		return -EINVAL;
> +
> +	return param_set_int(val, kp);
> +}
> +
> +
>   static inline bool
>   isert_prot_cmd(struct isert_conn *conn, struct se_cmd *cmd)
>   {
> @@ -101,7 +126,7 @@ isert_create_qp(struct isert_conn *isert_conn,
>   	attr.cap.max_send_wr = ISERT_QP_MAX_REQ_DTOS + 1;
>   	attr.cap.max_recv_wr = ISERT_QP_MAX_RECV_DTOS + 1;
>   	factor = rdma_rw_mr_factor(device->ib_device, cma_id->port_num,
> -				   ISCSI_ISER_MAX_SG_TABLESIZE);
> +				   isert_sg_tablesize);
>   	attr.cap.max_rdma_ctxs = ISCSI_DEF_XMIT_CMDS_MAX * factor;
>   	attr.cap.max_send_sge = device->ib_device->attrs.max_send_sge;
>   	attr.cap.max_recv_sge = 1;
> diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
> index 7fee4a65e181..90ef215bf755 100644
> --- a/drivers/infiniband/ulp/isert/ib_isert.h
> +++ b/drivers/infiniband/ulp/isert/ib_isert.h
> @@ -65,6 +65,12 @@
>    */
>   #define ISER_RX_SIZE		(ISCSI_DEF_MAX_RECV_SEG_LEN + 1024)
>   
> +/* Default I/O size is 1MB */
> +#define ISCSI_ISER_SG_TABLESIZE 256

Maybe name it ISCSI_ISER_DEF_SG_TABLESIZE

Otherwise,

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>