From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>, Dave Taht <dave.taht@gmail.com>,
Jonathan Morton <chromatix99@gmail.com>,
brouer@redhat.com
Subject: Re: [PATCH net-next] fq_codel: add batch ability to fq_codel_drop()
Date: Mon, 2 May 2016 18:00:36 +0200 [thread overview]
Message-ID: <20160502180036.25bebdfe@redhat.com> (raw)
In-Reply-To: <1462199668.5535.239.camel@edumazet-glaptop3.roam.corp.google.com>
On Mon, 02 May 2016 07:34:28 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Mon, 2016-05-02 at 09:49 +0200, Jesper Dangaard Brouer wrote:
>
> > What about using bulk free of SKBs here?
> >
> > There is a very high probability that we are hitting SLUB slowpath,
> > which involves an expensive locked cmpxchg_double per packet. Instead
> > we can amortize this cost via kmem_cache_free_bulk().
> >
> > Maybe extend kfree_skb_list() to hide the slab/kmem_cache call?
>
> Sounds tricky, because of skb destructors. skb are complex objects.
>
> For each skb, need to free the frags, skb->head, and skb.
It is not that complicated, inside kfree_skb_list(), we just call
skb_release_all(skb) on each SKB first, and then bulk free the SKB's
themselves in the end. Example see, _kfree_skb_defer().
The question is where to store the SKB array needed by kmem_cache_free_bulk.
The easy option is just to use the stack of kfree_skb_list(), but we
have to be careful about the stack size, it might not be so good
because skb_release_all() can be deep and via skb_release_data() invoke
kfree_skb_list() a second time.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2016-05-02 16:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-01 23:47 [PATCH net-next] fq_codel: add batch ability to fq_codel_drop() Eric Dumazet
2016-05-02 7:49 ` Jesper Dangaard Brouer
2016-05-02 14:34 ` Eric Dumazet
2016-05-02 16:00 ` Jesper Dangaard Brouer [this message]
2016-05-02 16:12 ` Eric Dumazet
2016-05-02 17:15 ` Jesper Dangaard Brouer
2016-05-03 1:07 ` Dave Taht
2016-05-03 16:47 ` David Miller
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