Messages in this thread | | | Date | Wed, 26 Feb 2014 00:48:57 +0200 | Subject | Re: [PATCH] mlx4: Use GFP_NOFS calls during the ipoib TX path when creating the QP | From | Or Gerlitz <> |
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On Wed, Feb 26, 2014 at 12:40 AM, Jiri Kosina <jkosina@suse.cz> wrote: > 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
Still, even if different, I still don't see why not use datagram mode if the problem hits you only for connected mode. E.g datagram mode supports LSO/GRO and TX/RX checksum offloads which should cover on the smaller MTU vs. connected mode
>> > 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.
Note that even when operating in connected mode, the ipoib net-device instance can speak in datagram mode with remote nodes who don't support connected mor and/or when sending multicast -- specifically ipoib_dev_init() does the setup of the TX ring. Maybe you can just try this out and see if it works?
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