From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH bpf-next v4 2/2] samples/bpf: Add xdp_sample_pkts example Date: Wed, 6 Jun 2018 13:33:49 +0200 Message-ID: <20180606133349.401f7cfe@redhat.com> References: <152821020087.23694.8231039605257373797.stgit@alrua-kau> <152821020092.23694.4231922206556589059.stgit@alrua-kau> <20180605152434.0149b8a7@cakuba.netronome.com> <87vaawyy8v.fsf@toke.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Cc: brouer@redhat.com, Jakub Kicinski , netdev@vger.kernel.org, Martin KaFai Lau To: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36558 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751536AbeFFLdx (ORCPT ); Wed, 6 Jun 2018 07:33:53 -0400 In-Reply-To: <87vaawyy8v.fsf@toke.dk> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 06 Jun 2018 13:01:52 +0200 Toke Høiland-Jørgensen wrote: > Jakub Kicinski writes: > > > On Tue, 05 Jun 2018 16:50:00 +0200, Toke Høiland-Jørgensen wrote: > >> Add an example program showing how to sample packets from XDP using the > >> perf event buffer. The example userspace program just prints the ethernet > >> header for every packet sampled. > >> > >> Signed-off-by: Toke Høiland-Jørgensen > > > >> diff --git a/samples/bpf/xdp_sample_pkts_kern.c b/samples/bpf/xdp_sample_pkts_kern.c > >> new file mode 100644 > >> index 000000000000..4560522ca015 > >> --- /dev/null > >> +++ b/samples/bpf/xdp_sample_pkts_kern.c > >> @@ -0,0 +1,62 @@ > >> +#include > >> +#include > >> +#include > >> +#include "bpf_helpers.h" > >> + > >> +#define SAMPLE_SIZE 64ul > >> +#define MAX_CPUS 24 > > > > That may be a lil' too few for modern HW with hyper-threading on ;) > > My development machine says: > > > > $ ncpus > > 28 > > > > 128, maybe? > > What? 24 CPUs should be enough for everyone, surely? ;) > > (I just took twice the number of CPUs in my largest machine; but fair > point, other people have access to more expensive toys I guess... will fix) > > >> +#define bpf_printk(fmt, ...) \ > >> +({ \ > >> + char ____fmt[] = fmt; \ > >> + bpf_trace_printk(____fmt, sizeof(____fmt), \ > >> + ##__VA_ARGS__); \ > >> +}) > >> + > >> +struct bpf_map_def SEC("maps") my_map = { > >> + .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY, > >> + .key_size = sizeof(int), > >> + .value_size = sizeof(u32), > >> + .max_entries = MAX_CPUS, > >> +}; I agree, we should increase it to something larger than 24, just to avoid people getting surprised, but this is only sample code. At some point I want us to add another example, that show how to adjust this runtime, which is actually possible with bpf_load.c via a map callback that Martin added. I've not look at how libbpf can support this. I do have sample code[1] that could be adjusted to do this, but I don't want to create dependencies to bpf_load.c, as we all agree that everything should be moved to use libbpf (tools/lib/bpf). [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/xdp_ddos01_blacklist_user.c#L186-L218 -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer