From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: john Fastabend <john.r.fastabend@intel.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
eric Dumazet <edumazet@google.com>,
brouer@redhat.com,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: qdisc running
Date: Mon, 20 Oct 2014 18:17:56 +0200 [thread overview]
Message-ID: <20141020181756.2c8f33b9@redhat.com> (raw)
In-Reply-To: <54440FFA.40307@mojatatu.com>
On Sun, 19 Oct 2014 15:24:42 -0400 Jamal Hadi Salim <jhs@mojatatu.com> wrote:
> Jesper,
>
> You asked at the meeting the point to qdisc running.
Talking about __QDISC___STATE_RUNNING see slide 9/16:
http://people.netfilter.org/hawk/presentations/LinuxPlumbers2014/performance_tx_qdisc_bulk_LPC2014.pdf
> Original intent is to allow only one cpu to enter the lower half of the
> qdisc path. IOW, if one cpu was already in the qdisc then that guy
> could be used to dequeue packets. i.e this is good for batching.
> Original idea was Herbert's with major improvement from Eric
> and a small one from me.
I guess it is good for our recent dequeue batching. But I think/hope we
can come up with a scheme that does not requires 6 lock/unlock
operations (as illustrated on slide 9).
John and I have talked about doing a lockless qdisc, but maintaining
this __QDISC___STATE_RUNNING in a lockless scenario, would cost us
extra atomic ops...
Are we still sure, that this model of only allowing a single CPU in the
dequeue path, is still the best solution? (The TXQ lock should already
protect several CPUs in this code path).
> For history of different tried approaches look at:
> Look at slide 2:
> http://vger.kernel.org/netconf2011_slides/jamal_netconf2011.pdf
I can see that you really needed the budget/fairness in the dequeue
loop, that we recently mangled with.
> then download the **amazing** flash animations which describe
> that history.
> http://vger.kernel.org/netconf2011_slides/netconf-2011-flash.tgz
>
> Follow the bullets in slide2 and map to the flash animations.
What tool do I use to play these SWF files? (I tried VLC but no luck).
> If you go over them, you'll see it is still needed.
Too bad, I would like to avoid the second
> I think someone oughta put those **amazing** animations on some
> website;->
I hope someone else can pick that up ;-)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Sr. Network Kernel Developer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2014-10-20 16:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-19 19:24 qdisc running Jamal Hadi Salim
2014-10-20 16:17 ` Jesper Dangaard Brouer [this message]
2014-10-20 22:17 ` Jamal Hadi Salim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20141020181756.2c8f33b9@redhat.com \
--to=brouer@redhat.com \
--cc=edumazet@google.com \
--cc=herbert@gondor.apana.org.au \
--cc=jhs@mojatatu.com \
--cc=john.r.fastabend@intel.com \
--cc=mathieu.desnoyers@efficios.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.