From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4CCAFC00449 for ; Fri, 5 Oct 2018 06:46:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0C69520834 for ; Fri, 5 Oct 2018 06:46:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0C69520834 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727878AbeJENoI (ORCPT ); Fri, 5 Oct 2018 09:44:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53002 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727198AbeJENoI (ORCPT ); Fri, 5 Oct 2018 09:44:08 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8AFA2A4D29; Fri, 5 Oct 2018 06:46:52 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-149.rdu2.redhat.com [10.10.120.149]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6071969FAF; Fri, 5 Oct 2018 06:46:51 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20181005020316.7cqlcfkedhamwhtt@ast-mbp.dhcp.thefacebook.com> References: <20181005020316.7cqlcfkedhamwhtt@ast-mbp.dhcp.thefacebook.com> <20181004171925.6neebizw4xmpjhv6@ast-mbp.dhcp.thefacebook.com> <153864184110.20296.16498481420320274305.stgit@warthog.procyon.org.uk> <25668.1538672073@warthog.procyon.org.uk> <5213.1538695482@warthog.procyon.org.uk> To: Alexei Starovoitov Cc: dhowells@redhat.com, David Ahern , netdev@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] udp: Add tracepoints to monitor skbs going in and out of a UDP socket MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <9723.1538722010.1@warthog.procyon.org.uk> Date: Fri, 05 Oct 2018 07:46:50 +0100 Message-ID: <9724.1538722010@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 05 Oct 2018 06:46:52 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alexei Starovoitov wrote: > - kprobes at the top of the function don't use traps and they've been > optimized over the years to have very low overhead To quote kprobes.txt: How Does a Kprobe Work? ----------------------- When a kprobe is registered, Kprobes makes a copy of the probed instruction and replaces the first byte(s) of the probed instruction with a breakpoint instruction (e.g., int3 on i386 and x86_64). Perhaps the docs need updating. However, for my purposes, tracepoints are easier. Anyway, as I said, I don't feel that strongly about the patch. It was useful for me, and I thought it might be useful for other people. David