From: David Miller <davem@davemloft.net>
To: brouer@redhat.com
Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com,
hannes@stressinduktion.org, dborkman@redhat.com,
dave.taht@gmail.com
Subject: Re: [PATCH] net_sched: restore qdisc quota fairness limits after bulk dequeue
Date: Thu, 09 Oct 2014 19:12:48 -0400 (EDT) [thread overview]
Message-ID: <20141009.191248.516797236807606254.davem@davemloft.net> (raw)
In-Reply-To: <20141009101640.26713.80729.stgit@dragon>
From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Thu, 09 Oct 2014 12:18:10 +0200
> Restore the quota fairness between qdisc's, that we broke with commit
> 5772e9a346 ("qdisc: bulk dequeue support for qdiscs with TCQ_F_ONETXQUEUE").
>
> Before that commit, the quota in __qdisc_run() were in packets as
> dequeue_skb() would only dequeue a single packet, that assumption
> broke with bulk dequeue.
>
> We choose not to account for the number of packets inside the TSO/GSO
> packets (accessable via "skb_gso_segs"). As the previous fairness
> also had this "defect". Thus, GSO/TSO packets counts as a single
> packet.
>
> Further more, we choose to slack on accuracy, by allowing a bulk
> dequeue try_bulk_dequeue_skb() to exceed the "packets" limit, only
> limited by the BQL bytelimit. This is done because BQL prefers to get
> its full budget for appropriate feedback from TX completion.
>
> In future, we might consider reworking this further and, if it allows,
> switch to a time-based model, as suggested by Eric. Right now, we only
> restore old semantics.
>
> Joint work with Eric, Hannes, Daniel and Jesper. Hannes wrote the
> first patch in cooperation with Daniel and Jesper. Eric rewrote the
> patch.
>
> Fixes: 5772e9a346 ("qdisc: bulk dequeue support for qdiscs with TCQ_F_ONETXQUEUE")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Looks fantastic, thanks everyone.
prev parent reply other threads:[~2014-10-09 23:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-09 10:18 [PATCH] net_sched: restore qdisc quota fairness limits after bulk dequeue Jesper Dangaard Brouer
2014-10-09 23:12 ` David Miller [this message]
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