Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933268AbcDYTWg (ORCPT ); Mon, 25 Apr 2016 15:22:36 -0400 Received: from mail.kernel.org ([198.145.29.136]:59087 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932821AbcDYTWe (ORCPT ); Mon, 25 Apr 2016 15:22:34 -0400 Date: Mon, 25 Apr 2016 16:22:29 -0300 From: Arnaldo Carvalho de Melo To: Alexei Starovoitov Cc: David Ahern , Arnaldo Carvalho de Melo , Peter Zijlstra , Frederic Weisbecker , Ingo Molnar , Adrian Hunter , Brendan Gregg , Alexander Shishkin , Alexei Starovoitov , He Kuang , Jiri Olsa , Masami Hiramatsu , Milian Wolff , Namhyung Kim , Stephane Eranian , Thomas Gleixner , Vince Weaver , Wang Nan , Zefan Li , Linux Kernel Mailing List Subject: Re: [PATCH/RFC v2] perf core: Allow setting up max frame stack depth via sysctl Message-ID: <20160425192229.GC25218@kernel.org> References: <20160420224730.GX3677@kernel.org> <20160420230410.GA41736@ast-mbp.thefacebook.com> <20160422205232.GB7004@kernel.org> <571AA02B.90107@gmail.com> <20160422221806.GA62857@ast-mbp.thefacebook.com> <20160425161425.GA25218@kernel.org> <20160425162706.GB25218@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160425162706.GB25218@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2647 Lines: 73 Em Mon, Apr 25, 2016 at 01:27:06PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Mon, Apr 25, 2016 at 01:14:25PM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Fri, Apr 22, 2016 at 03:18:08PM -0700, Alexei Starovoitov escreveu: > > > right... and looking into it further, realized that the patch is broken, > > > since get_callchain_entry() is doing: > > > return &entries->cpu_entries[cpu][*rctx]; > > > whereas it should be dynamic offset based on sysctl_perf_event_max_stack*8 > > > So definitely needs another respin. > struct perf_callchain_entry { > __u64 nr; > __u64 ip[0]; /* /proc/sys/kernel/perf_event_max_stack */ > }; > But perf_callchain_entry->ip is not a pointer... Got it ;-\ This is what I am building now, a patch on top of the previous, that will be combined and sent as v3, if I don't find any more funnies: diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 6fe77349fa9d..40657892a7e0 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -20,11 +20,10 @@ struct callchain_cpus_entries { int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; -static size_t perf_callchain_entry__sizeof(void) -{ - return sizeof(struct perf_callchain_entry) + - sizeof(__u64) * sysctl_perf_event_max_stack; -} +#define __perf_callchain_entry_size(entries) \ + (sizeof(struct perf_callchain_entry) + sizeof(__u64) * entries) + +static size_t perf_callchain_entry_size __read_mostly = __perf_callchain_entry_size(PERF_MAX_STACK_DEPTH); static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); static atomic_t nr_callchain_events; @@ -81,7 +80,7 @@ static int alloc_callchain_buffers(void) if (!entries) return -ENOMEM; - size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS; + size = perf_callchain_entry_size * PERF_NR_CONTEXTS; for_each_possible_cpu(cpu) { entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, @@ -155,7 +154,8 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx) cpu = smp_processor_id(); - return &entries->cpu_entries[cpu][*rctx]; + return (((void *)&entries->cpu_entries[cpu][0]) + + (*rctx * perf_callchain_entry_size)); } static void @@ -236,10 +236,12 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write, return ret; mutex_lock(&callchain_mutex); - if (atomic_read(&nr_callchain_events)) + if (atomic_read(&nr_callchain_events)) { ret = -EBUSY; - else + } else { sysctl_perf_event_max_stack = new_value; + perf_callchain_entry_size = __perf_callchain_entry_size(new_value); + } mutex_unlock(&callchain_mutex);