On Mon, 13 Jun 2016 20:21:50 -0700
Eric Dumazet <eduma...@google.com> wrote:
> qdisc are changed under RTNL protection and often
> while blocking BH and root qdisc spinlock.
>
> When lots of skbs need to be dropped, we free
> them under these locks causing TX/RX freezes,
> and more generally latency spikes.
>
> This commit adds rtnl_kfree_skbs(), used to queue
> skbs for deferred freeing.
>
> Actual freeing happens right after RTNL is released,
> with appropriate scheduling points.
>
> rtnl_qdisc_drop() can also be used in place
> of disc_drop() when RTNL is held.
>
> qdisc_reset_queue() and __qdisc_reset_queue() get
> the new behavior, so standard qdiscs like pfifo, pfifo_fast...
> have their ->reset() method automatically handled.
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> ---
> include/linux/rtnetlink.h | 5 +++--
> include/net/sch_generic.h | 16 ++++++++++++----
> net/core/rtnetlink.c | 22 ++++++++++++++++++++++
> net/sched/sch_generic.c | 2 +-
> 4 files changed, 38 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
> index c006cc900c44..2daece8979f7 100644
> --- a/include/linux/rtnetlink.h
> +++ b/include/linux/rtnetlink.h
[...]
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index d69c4644f8f2..eb49ca24274a 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -71,9 +71,31 @@ void rtnl_lock(void)
> }
> EXPORT_SYMBOL(rtnl_lock);
>
> +static struct sk_buff *defer_kfree_skb_list;
> +void rtnl_kfree_skbs(struct sk_buff *head, struct sk_buff *tail)
> +{
> + if (head && tail) {
> + tail->next = defer_kfree_skb_list;
> + defer_kfree_skb_list = head;
> + }
> +}
> +EXPORT_SYMBOL(rtnl_kfree_skbs);
> +
> void __rtnl_unlock(void)
> {
> + struct sk_buff *head = defer_kfree_skb_list;
> +
> + defer_kfree_skb_list = NULL;
> +
> mutex_unlock(&rtnl_mutex);
> +
> + while (head) {
> + struct sk_buff *next = head->next;
> +
> + kfree_skb(head);
> + cond_resched();
> + head = next;
> + }
> }
This looks a lot like kfree_skb_list()....
What about bulk free'ing SKBs here?
--
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
