From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>
Cc: saeedm@mellanox.com, gerlitz.or@gmail.com, eugenia@mellanox.com,
Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [net-next PATCH V1 3/3] net: warn on napi_alloc_skb being called in wrong context
Date: Mon, 9 May 2016 16:53:50 +0300 [thread overview]
Message-ID: <50c0ae0c-2382-42ea-998b-f5c641e5db4a@cogentembedded.com> (raw)
In-Reply-To: <20160509134439.3573.97841.stgit@firesoul>
Hello.
On 5/9/2016 4:44 PM, Jesper Dangaard Brouer wrote:
> It have always been required to call napi_alloc_skb from NAPI/softirq
It has.
> context, which implies running with local_bh_disable'ed. Thus, this
Not local_bh_disable'd?
> code path should already be well tested. But recent SKB bulk changes
> introduced will make this more volatile and bugs more subtle, if this
> is violated.
>
> To catch any driver violating this add a loud WARN_ON.
>
> Performance wise, I do worry about adding this runtime check code into
> the hotpath, of this highly optimized function call. I've
Hot path? My spellchecker trips here.
> micro-benchmarked it with both IP-forwarding and local UDP delivery,
> and didn't see any regressions. It does adds extra code size (icache).
>
> add/remove: 0/0 grow/shrink: 1/0 up/down: 43/0 (43)
> function old new delta
> __napi_alloc_skb 461 504 +43
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
[...]
MBR, Sergei
next prev parent reply other threads:[~2016-05-09 13:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 13:44 [net-next PATCH V1 0/3] net: enable use of kmem_cache_alloc_bulk in network stack Jesper Dangaard Brouer
2016-05-09 13:44 ` [net-next PATCH V1 1/3] net: bulk alloc and reuse of SKBs in NAPI context Jesper Dangaard Brouer
2016-05-09 16:20 ` Alexander Duyck
2016-05-09 19:59 ` Jesper Dangaard Brouer
2016-05-09 20:46 ` Alexander Duyck
2016-05-10 9:29 ` Jesper Dangaard Brouer
2016-05-10 12:30 ` Jesper Dangaard Brouer
2016-05-10 13:48 ` Eric Dumazet
2016-05-10 14:48 ` Jesper Dangaard Brouer
2016-05-10 15:44 ` Eric Dumazet
2016-05-10 17:46 ` Alexander Duyck
2016-05-09 13:44 ` [net-next PATCH V1 2/3] mlx4: use napi_alloc_skb API to get SKB bulk allocations Jesper Dangaard Brouer
2016-05-09 16:47 ` Alexander Duyck
2016-05-09 20:05 ` Jesper Dangaard Brouer
2016-05-09 13:44 ` [net-next PATCH V1 3/3] net: warn on napi_alloc_skb being called in wrong context Jesper Dangaard Brouer
2016-05-09 13:53 ` Sergei Shtylyov
2016-05-09 13:53 ` Sergei Shtylyov [this message]
2016-05-09 16:33 ` Alexander Duyck
2016-05-09 20:03 ` Jesper Dangaard Brouer
2016-05-20 8:14 ` [net-next PATCH V1 0/3] net: enable use of kmem_cache_alloc_bulk in network stack Jesper Dangaard Brouer
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