netdev - Re: [PATCH] mlx4: Use GFP_NOFS calls during the ipoib TX path when creating the QP

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Message-ID: <alpine.LNX.2.00.1402252338480.5180@pobox.suse.cz>
Date:	Tue, 25 Feb 2014 23:40:35 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Or Gerlitz <or.gerlitz@...il.com>
cc:	Roland Dreier <roland@...nel.org>, Amir Vadai <amirv@...lanox.com>,
	Eli Cohen <eli@....mellanox.co.il>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>,
	Mel Gorman <mgorman@...e.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mlx4: Use GFP_NOFS calls during the ipoib TX path when
 creating the QP

On Wed, 26 Feb 2014, Or Gerlitz wrote:

> >> And what happens if you use IPoIB datagram mode, is/why the patch is
> >> needed there?
> 
> > I admittedly am no infiniband expert, but my understanding is that in
> > principle Connected/Datagram mode is about MTU and checksum offloading,
> 
> yes, the differences between the mode relate to these aspects, however

Thanks for confirming.

> > but the TX path is the same. Please correct me if I am wrong.
> 
> no, note that your patch only touched drivers/infiniband/ulp/ipoib/ipoib_cm.c
> which is basically compiled out if you set CONFIG_INFINIBAND_IPOIB_CM,
> so surely the TX path for the datagram vs. connected modes are
> different.

Yes, but for datagram mode, the tx_ring is allocated in a completely 
different way (not from kworker), so this might be a non-issue, right? I 
will have to look into it more deeply to be really sure; if you can 
provide your insight, that'd be helpful.

-- 
Jiri Kosina
SUSE Labs
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