Re: [PATCH 1/9] IB/ipoib: factor out ah flushing

[Erez Shitrit <erezsh-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 3/16/2015 6:06 PM, Doug Ledford wrote:
>> On Mar 16, 2015, at 8:24 AM, Erez Shitrit <erezsh-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org> wrote:
>>
>> On 3/15/2015 8:42 PM, Doug Ledford wrote:
>>>> Doug, ten days and no response from you... lets finalize the review on
>>>> this series so we have it safely done for 4.1 -- on top of it Erez
>>>> prepares a set of IPoIB fixes from our internal tree and we want that
>>>> for 4.1 too. Please address.
>>> I didn’t have much to say here.  I said that mthca can have card resources freed by this call, which is backed up by this code in mthca_ah.c
>>>
>>> int mthca_destroy_ah(struct mthca_dev *dev, struct mthca_ah *ah)
>>> {
>>>          switch (ah->type) {
>>>          case MTHCA_AH_ON_HCA:
>>>                  mthca_free(&dev->av_table.alloc,
>>>                             (ah->avdma - dev->av_table.ddr_av_base) /
>>>                             MTHCA_AV_SIZE);
>>>                  break;
>>>
>>>
>>> I’m not entirely sure how Erez missed that, but it’s there and it’s what gets called when we destroy an ah (depending on the card of course).  So, that represents one case where freeing the resources in a non-lazy fashion has a direct benefit.  And there is no cited drawback to freeing the resources in a non-lazy fashion on a net event, so I don’t see what there is to discuss further on the issue.
>> sorry, but i still don't see the connection to the device type.
>> It will be deleted/freed with the regular flow, like it does in the rest of the life cycle cases of the ah (in neigh_dtor, path_free, etc.), so why here it should be directly after the event?
> Because it’s the right thing to do.  The only reason to do lazy deletion is when there is a performance benefit to batching.  There is no performance benefit to batching here.  And because on certain hardware the action frees resources on the card, which are limited, doing non-lazy deletion can be beneficial.  Given that there is no downside to doing the deletions in a non-lazy fashion, and that there can be an upside depending on hardware, there is no reason to stick with the lazy deletions.
OK, i understand your point, not sure why it is not always with the ah 
deletion, anyway it is harmless here.

> —
> Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> 	GPG Key ID: 0E572FDD
>
>
>
>
>

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