netdev - Re: [PATCH v2] net: use bulk free in kfree_skb

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Date:   Mon, 25 Mar 2019 10:35:35 +0100
From:   Felix Fietkau <nbd@....name>
To:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, brouer@...hat.com, fw@...len.de
Subject: Re: [PATCH v2] net: use bulk free in kfree_skb_list

On 2019-03-25 10:31, Eric Dumazet wrote:
> 
> 
> On 03/25/2019 02:09 AM, Felix Fietkau wrote:
>> On 2019-03-25 09:51, Eric Dumazet wrote:
>>>
>>>
>>> On 03/24/2019 09:56 AM, Felix Fietkau wrote:
>>>> Since we're freeing multiple skbs, we might as well use bulk free to save a
>>>> few cycles. Use the same conditions for bulk free as in napi_consume_skb.
>>>>
>>>
>>> I do not believe kfree_skb_list() is used in the fast path, so do we really
>>> need to make it so complex ?
>> mac80211 uses it to free the fraglist from A-MSDU aggregated packets in
>> the tx status path. That's one fast path where it gets used right now
>> and the reason it was showing up in my perf traces.
> 
> This is not drop monitor friendly then....
> 
> TX completion should use consume_skb() or dev_kfree_skb()
> 
> BTW, I wonder what drop-monitor signal bulk free is sending ?
Good point about the drop monitor. Would you prefer that I replace this
patch with one that adds a consume_skb_list function and another one
that makes mac80211 use it?

- Felix