scsi_transport_fc: FPIN LI statistics

From: James Smart <james.smart@broadcom.com>
To: Nilesh Javali <njavali@marvell.com>, Shyam Sundar <ssundar@marvell.com>
Cc: linux-scsi@vger.kernel.org,
	GR-QLogic-Storage-Upstream@marvell.com,
	Himanshu Madhani <himanshu.madhani@oracle.com>
Subject: scsi_transport_fc: FPIN LI statistics
Date: Fri, 28 May 2021 14:49:32 -0700	[thread overview]
Message-ID: <b472606d-e67c-66f1-06d1-ecc5fbb2071a@broadcom.com> (raw)
In-Reply-To: <20201021092715.22669-4-njavali@marvell.com>

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Nilesh, Shyam,

I'm looking at commit 3dcfe0de5a97.  When we increment stats, we are 
incrementing by the event_count:
> +static void
> +fc_li_stats_update(struct fc_fn_li_desc *li_desc,
> +		   struct fc_fpin_stats *stats)
> +{
> +	stats->li += be32_to_cpu(li_desc->event_count);
> +	switch (be16_to_cpu(li_desc->event_type)) {
> +	case FPIN_LI_UNKNOWN:
> +		stats->li_failure_unknown +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_LINK_FAILURE:
> +		stats->li_link_failure_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_LOSS_OF_SYNC:
> +		stats->li_loss_of_sync_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_LOSS_OF_SIG:
> +		stats->li_loss_of_signals_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_PRIM_SEQ_ERR:
> +		stats->li_prim_seq_err_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_INVALID_TX_WD:
> +		stats->li_invalid_tx_word_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_INVALID_CRC:
> +		stats->li_invalid_crc_count +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	case FPIN_LI_DEVICE_SPEC:
> +		stats->li_device_specific +=
> +		    be32_to_cpu(li_desc->event_count);
> +		break;
> +	}
> +}

I'm wondering if this is really what we want.   Event_count is the 
minimum # of events that must occur before an FPIN is sent.  Thus, its 
not the actual number of events, and could be significantly off (low).   
Are we ok with that ?  Do we set the wrong impression with the user 
(here's a count, but its not necessary accurate) ?    Would it be better 
to simply count the # of FPINs (increment by 1 each time) ?

-- james

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