From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [net-next PATCH 1/4] samples/bpf: adjust rlimit RLIMIT_MEMLOCK for traceex2, tracex3 and tracex4 Date: Wed, 3 May 2017 10:12:13 +0200 Message-ID: <20170503101213.7eece6c9@redhat.com> References: <149372826543.22268.3617359219409721129.stgit@firesoul> <149372831091.22268.12527267276516941574.stgit@firesoul> <20170503005314.7oovr764r3e4elzd@ast-mbp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: kafai@fb.com, netdev@vger.kernel.org, eric@regit.org, Daniel Borkmann , brouer@redhat.com To: Alexei Starovoitov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51968 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751539AbdECIMU (ORCPT ); Wed, 3 May 2017 04:12:20 -0400 In-Reply-To: <20170503005314.7oovr764r3e4elzd@ast-mbp> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2 May 2017 17:53:16 -0700 Alexei Starovoitov wrote: > On Tue, May 02, 2017 at 02:31:50PM +0200, Jesper Dangaard Brouer wrote: > > Needed to adjust max locked memory RLIMIT_MEMLOCK for testing these bpf samples > > as these are using more and larger maps than can fit in distro default 64Kbytes limit. > > > > Signed-off-by: Jesper Dangaard Brouer > ... > > + struct rlimit r = {1024*1024, RLIM_INFINITY}; > ... > > + struct rlimit r = {1024*1024, RLIM_INFINITY}; > > why magic numbers? > All other samples do > struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY}; I just wanted to provide some examples showing that it is possible to set some reasonable limit. The RLIM_INFINITY setting is basically just disabling the kernels memory limit checks, and it is sort of a bad coding pattern (that people will copy) as the two example programs does not need much. > > + if (setrlimit(RLIMIT_MEMLOCK, &r)) { > > + perror("setrlimit(RLIMIT_MEMLOCK)"); > > ip_tunnel.c test does: > perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)"); > Few others do: > assert(!setrlimit(RLIMIT_MEMLOCK, &r)); > and the rest just: > setrlimit(RLIMIT_MEMLOCK, &r); > > We probalby need to move this to a helper. > > > + struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY}; > > here it's consistent :) > > > + if (setrlimit(RLIMIT_MEMLOCK, &r)) { > > + perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)"); > > but with different perror ? > Let's do a common helper for all? Sure, it makes sense to streamline this into a helper, just not in this patchset ;-) Lets do that later... And I would argue that this helper should allow users to specify some expected/reasonable memory usage size, as the kernel side checks would then provide some value, instead of being effectively disabled. I can easily imagine someone increasing a _kern.c hash map max size to 100 million, without realizing that this can OOM the machine. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer