From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Fastabend Subject: Re: [PATCH net-next] tc: fix tc actions in case of shared skb Date: Tue, 14 Jul 2015 17:58:15 -0700 Message-ID: <55A5B027.70604@gmail.com> References: <55A41CE9.8050907@plumgrid.com> <55A425C4.60301@iogearbox.net> <55A43B26.1010009@plumgrid.com> <20150714.153422.914759715820927338.davem@davemloft.net> <55A59657.2050100@plumgrid.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: daniel@iogearbox.net, jhs@mojatatu.com, jiri@resnulli.us, netdev@vger.kernel.org To: Alexei Starovoitov , David Miller Return-path: Received: from mail-oi0-f43.google.com ([209.85.218.43]:32911 "EHLO mail-oi0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751241AbbGOA6D (ORCPT ); Tue, 14 Jul 2015 20:58:03 -0400 Received: by oige126 with SMTP id e126so18302071oig.0 for ; Tue, 14 Jul 2015 17:58:02 -0700 (PDT) In-Reply-To: <55A59657.2050100@plumgrid.com> Sender: netdev-owner@vger.kernel.org List-ID: On 15-07-14 04:08 PM, Alexei Starovoitov wrote: > On 7/14/15 3:34 PM, David Miller wrote: >>>>> 1 get rid of burst hack for both RX and TX in pktgen (kills >>>>> >>>performance) >> #1 is a serious consideration if you don't come up with better ideas, >> since an optimization is for nothing if it knowingly breaks things. > > I've dug up the pktgen source from 2002 and see: > atomic_inc(&skb->users); > odev->hard_start_xmit(skb, odev); > so it did this trick forever. > Looks like it's a fundamental way how pktgen was working > and working still. Even when new 'burst' feature is not used, > pktgen still increments skb->users to hold skb. > At present I don't have good ideas how to redesign pktgen > and since apparently no one noticed this tc_action+pktgen > breakage for years, it's probably ok to leave everything as-is until > better ideas come. I'm not giving up yet. Just ran out of ideas. > Right and we hit this issue when pktgen is run over any stacked device with clone_skb set. I've always put it in the don't do this category but a fix would be nice. > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html