From owner-freebsd-current@FreeBSD.ORG Tue Jun 10 03:13:38 2014 Return-Path: Delivered-To: current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id A6AE097F; Tue, 10 Jun 2014 03:13:38 +0000 (UTC) Received: from torment.daemoninthecloset.org (torment.daemoninthecloset.org [94.242.209.234]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "torment.daemoninthecloset.org", Issuer "daemoninthecloset.org" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 648EE2F9E; Tue, 10 Jun 2014 03:13:38 +0000 (UTC) Received: from sage.daemoninthecloset.org (cpe-72-177-8-109.austin.res.rr.com [72.177.8.109]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "sage.daemoninthecloset.org", Issuer "daemoninthecloset.org" (not verified)) by torment.daemoninthecloset.org (Postfix) with ESMTPS id 03F6F42C2546; Tue, 10 Jun 2014 05:04:52 +0200 (CEST) X-Virus-Scanned: amavisd-new at daemoninthecloset.org X-Virus-Scanned: amavisd-new at daemoninthecloset.org Date: Mon, 9 Jun 2014 22:03:56 -0500 (CDT) From: Bryan Venteicher To: John-Mark Gurney Message-ID: <100488220.4292.1402369436876.JavaMail.root@daemoninthecloset.org> In-Reply-To: <20140610000246.GW31367@funkthat.com> References: <20140610000246.GW31367@funkthat.com> Subject: Re: dhclient sucks cpu usage... MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.10.20] X-Mailer: Zimbra 8.0.2_GA_5569 (ZimbraWebClient - GC33 ([unknown])/8.0.2_GA_5569) Thread-Topic: dhclient sucks cpu usage... Thread-Index: fmMcJNl9h8hOdeWB79fYswL50E8uIA== Cc: current@FreeBSD.org, net@FreeBSD.org X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Jun 2014 03:13:38 -0000 Hi, ----- Original Message ----- > So, after finding out that nc has a stupidly small buffer size (2k > even though there is space for 16k), I was still not getting as good > as performance using nc between machines, so I decided to generate some > flame graphs to try to identify issues... (Thanks to who included a > full set of modules, including dtraceall on memstick!) > > So, the first one is: > https://www.funkthat.com/~jmg/em.stack.svg > > As I was browsing around, the em_handle_que was consuming quite a bit > of cpu usage for only doing ~50MB/sec over gige.. Running top -SH shows > me that the taskqueue for em was consuming about 50% cpu... Also pretty > high for only 50MB/sec... Looking closer, you'll see that bpf_mtap is > consuming ~3.18% (under ether_nh_input).. I know I'm not running tcpdump > or anything, but I think dhclient uses bpf to be able to inject packets > and listen in on them, so I kill off dhclient, and instantly, the taskqueue > thread for em drops down to 40% CPU... (transfer rate only marginally > improves, if it does) > > I decide to run another flame graph w/o dhclient running: > https://www.funkthat.com/~jmg/em.stack.nodhclient.svg > > and now _rxeof drops from 17.22% to 11.94%, pretty significant... > > So, if you care about performance, don't run dhclient... > Yes, I've noticed the same issue. It can absolutely kill performance in a VM guest. It is much more pronounced on only some of my systems, and I hadn't tracked it down yet. I wonder if this is fallout from the callout work, or if there was some bpf change. I've been using the kludgey workaround patch below. diff --git a/sys/net/bpf.c b/sys/net/bpf.c index cb3ed27..9751986 100644 --- a/sys/net/bpf.c +++ b/sys/net/bpf.c @@ -2013,9 +2013,11 @@ bpf_gettime(struct bintime *bt, int tstype, struct mbuf *m) return (BPF_TSTAMP_EXTERN); } } +#if 0 if (quality == BPF_TSTAMP_NORMAL) binuptime(bt); else +#endif getbinuptime(bt); return (quality); > -- > John-Mark Gurney Voice: +1 415 225 5579 > > "All that I will do, has been done, All that I have, has not." > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >