netdev - Re: [PATCH 11/12 -Rev2] IPoIB xmit API addition

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Message-ID: <20070722094136.GD7800@mellanox.co.il>
Date:	Sun, 22 Jul 2007 12:41:36 +0300
From:	"Michael S. Tsirkin" <mst@....mellanox.co.il>
To:	Krishna Kumar <krkumar2@...ibm.com>
Cc:	davem@...emloft.net, rdreier@...co.com, johnpol@....mipt.ru,
	Robert.Olsson@...a.slu.se, peter.p.waskiewicz.jr@...el.com,
	herbert@...dor.apana.org.au, gaagaan@...il.com,
	kumarkr@...ux.ibm.com, mcarlson@...adcom.com, jagana@...ibm.com,
	general@...ts.openfabrics.org, netdev@...r.kernel.org,
	tgraf@...g.ch, jeff@...zik.org, hadi@...erus.ca, kaber@...sh.net,
	mchan@...adcom.com, sri@...ibm.com
Subject: Re: [PATCH 11/12 -Rev2] IPoIB xmit API addition

> +	/*
> +	 * Handle skbs completion from tx_tail to wr_id. It is possible to
> +	 * handle WC's from earlier post_sends (possible multiple) in this
> +	 * iteration as we move from tx_tail to wr_id, since if the last
> +	 * WR (which is the one which had a completion request) failed to be
> +	 * sent for any of those earlier request(s), no completion
> +	 * notification is generated for successful WR's of those earlier
> +	 * request(s).
> +	 */

AFAIK a signalled WR will always generate a completion.
What am I missing?

> 
> +			/*
> +			 * Better error handling can be done here, like free
> +			 * all untried skbs if err == -ENOMEM. However at this
> +			 * time, we re-try all the skbs, all of which will
> +			 * likely fail anyway (unless device finished sending
> +			 * some out in the meantime). This is not a regression
> +			 * since the earlier code is not doing this either.
> +			 */

Are you retrying posting skbs? Why is this a good idea?
AFAIK, earlier code did not retry posting WRs at all.
The comment seems to imply that post send fails as a result of SQ overflow -
do you see SQ overflow errors in your testing?
AFAIK, IPoIB should never overflow the SQ.

-- 
MST
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