Re: SQ overflow seen running isert traffic with high block sizes

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Hi Shiraz & Co,

Thanks for the feedback.

On Mon, 2018-01-22 at 17:49 +0000, Saleem, Shiraz wrote:
> > Subject: Re: SQ overflow seen running isert traffic with high block sizes
> > 
> > 
> > First, would it be helpful to limit maximum payload size per I/O for consumers
> > based on number of iser-target sq hw sges..?
> > 
> Assuming data is not able to be fast registered as if virtually contiguous;
> artificially limiting the data size might not be the best solution.
> 
> But max SGEs does need to be exposed higher. Somewhere in the stack,
> there might need to be multiple WRs submitted or data copied.
> 

Sagi..?

> > diff --git a/drivers/target/iscsi/iscsi_target_configfs.c
> > b/drivers/target/iscsi/iscsi_target_configf
> > index 0ebc481..d8a4cc5 100644
> > --- a/drivers/target/iscsi/iscsi_target_configfs.c
> > +++ b/drivers/target/iscsi/iscsi_target_configfs.c
> > @@ -1553,6 +1553,7 @@ static void lio_release_cmd(struct se_cmd *se_cmd)
> >         .module                         = THIS_MODULE,
> >         .name                           = "iscsi",
> >         .node_acl_size                  = sizeof(struct iscsi_node_acl),
> > +       .max_data_sg_nents              = 32, /* 32 * PAGE_SIZE = MAXIMUM
> > TRANSFER LENGTH */
> >         .get_fabric_name                = iscsi_get_fabric_name,
> >         .tpg_get_wwn                    = lio_tpg_get_endpoint_wwn,
> >         .tpg_get_tag                    = lio_tpg_get_tag,
> > 
> 
> BTW, this is helping the SQ overflow issue.

Thanks for confirming as a possible work-around.

For reference, what is i40iw's max_send_sg reporting..?

Is max_data_sg_nents=32 + 4k pages = 128K the largest MAX TRANSFER
LENGTH to avoid consistent SQ overflow as-is with i40iw..?

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