Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756187AbaBFPqu (ORCPT ); Thu, 6 Feb 2014 10:46:50 -0500 Received: from mail-oa0-f42.google.com ([209.85.219.42]:43503 "EHLO mail-oa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751611AbaBFPqs (ORCPT ); Thu, 6 Feb 2014 10:46:48 -0500 MIME-Version: 1.0 In-Reply-To: <1388728091-18564-13-git-send-email-zheng.z.yan@intel.com> References: <1388728091-18564-1-git-send-email-zheng.z.yan@intel.com> <1388728091-18564-13-git-send-email-zheng.z.yan@intel.com> Date: Thu, 6 Feb 2014 16:46:47 +0100 Message-ID: Subject: Re: [PATCH 12/14] perf, x86: use LBR call stack to get user callchain From: Stephane Eranian To: "Yan, Zheng" Cc: LKML , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Andi Kleen Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 3, 2014 at 6:48 AM, Yan, Zheng wrote: > Haswell has a new feature that utilizes the existing Last Branch Record > facility to record call chains. When the feature is enabled, function > call will be collected as normal, but as return instructions are executed > the last captured branch record is popped from the on-chip LBR registers. > The LBR call stack facility can help perf to get call chains of progam > without frame pointer. > > This patch makes x86's perf_callchain_user() failback to LBR callstack > when there is no frame pointer in the user program. > > Signed-off-by: Yan, Zheng > --- > arch/x86/kernel/cpu/perf_event.c | 33 ++++++++++++++++++++++++++---- > arch/x86/kernel/cpu/perf_event_intel.c | 11 +++++++++- > arch/x86/kernel/cpu/perf_event_intel_lbr.c | 2 ++ > include/linux/perf_event.h | 1 + > 4 files changed, 42 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 49128e6..1509340 100644 > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -1965,12 +1965,28 @@ static unsigned long get_segment_base(unsigned int segment) > return get_desc_base(desc + idx); > } > > +static inline void > +perf_callchain_lbr_callstack(struct perf_callchain_entry *entry, > + struct perf_sample_data *data) > +{ > + struct perf_branch_stack *br_stack = data->br_stack; > + > + if (br_stack && br_stack->user_callstack) { > + int i = 0; > + while (i < br_stack->nr && entry->nr < PERF_MAX_STACK_DEPTH) { > + perf_callchain_store(entry, br_stack->entries[i].from); > + i++; > + } > + } > +} > + > #ifdef CONFIG_COMPAT > > #include > > static inline int > -perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry) > +perf_callchain_user32(struct perf_callchain_entry *entry, > + struct pt_regs *regs, struct perf_sample_data *data) > { > /* 32-bit process in 64-bit kernel. */ > unsigned long ss_base, cs_base; > @@ -1999,11 +2015,16 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry) > perf_callchain_store(entry, cs_base + frame.return_address); > fp = compat_ptr(ss_base + frame.next_frame); > } > + > + if (fp == compat_ptr(regs->bp)) > + perf_callchain_lbr_callstack(entry, data); > + > return 1; > } > #else > static inline int > -perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry) > +perf_callchain_user32(struct perf_callchain_entry *entry, > + struct pt_regs *regs, struct perf_sample_data *data) > { > return 0; > } > @@ -2033,12 +2054,12 @@ void perf_callchain_user(struct perf_callchain_entry *entry, > if (!current->mm) > return; > > - if (perf_callchain_user32(regs, entry)) > + if (perf_callchain_user32(entry, regs, data)) > return; > > while (entry->nr < PERF_MAX_STACK_DEPTH) { > unsigned long bytes; > - frame.next_frame = NULL; > + frame.next_frame = NULL; > frame.return_address = 0; > > bytes = copy_from_user_nmi(&frame, fp, sizeof(frame)); > @@ -2051,6 +2072,10 @@ void perf_callchain_user(struct perf_callchain_entry *entry, > perf_callchain_store(entry, frame.return_address); > fp = frame.next_frame; > } > + > + /* try LBR callstack if there is no frame pointer */ > + if (fp == (void __user *)regs->bp) > + perf_callchain_lbr_callstack(entry, data); > } > > /* > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c > index 722171c..8b7465c 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel.c > +++ b/arch/x86/kernel/cpu/perf_event_intel.c > @@ -1030,6 +1030,14 @@ static __initconst const u64 slm_hw_cache_event_ids > }, > }; > > +static inline bool intel_pmu_needs_lbr_callstack(struct perf_event *event) > +{ > + if ((event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) && > + (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)) > + return true; > + return false; > +} > + > static void intel_pmu_disable_all(void) > { > struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); > @@ -1398,7 +1406,8 @@ again: > > perf_sample_data_init(&data, 0, event->hw.last_period); > > - if (has_branch_stack(event)) > + if (has_branch_stack(event) || > + (event->ctx->task && intel_pmu_needs_lbr_callstack(event))) Isn't event->ctx->task redundant here. I thought you were already allowing LBR_CALLSTACK only for per-process events. That should be checked during setup, no need to do it for each interrupt. Also it would be nicer to have: if (needs_lbr_stack(event)) data.br_stack = &cpuc->lbr_stack; And you'd hide the two tests in that needs_lbr_stack() inline: has_branch_stack() and has_lbr_callstack(). That would be better for the eyes.... > > if (perf_event_overflow(event, &data, regs)) > diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c > index 51e1842..08e3ba1 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c > +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c > @@ -718,6 +718,8 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc) > int i, j, type; > bool compress = false; > > + cpuc->lbr_stack.user_callstack = branch_user_callstack(br_sel); > + > /* if sampling all branches, then nothing to filter */ > if ((br_sel & X86_BR_ALL) == X86_BR_ALL) > return; > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index c442276..d2f0488 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -74,6 +74,7 @@ struct perf_raw_record { > * recent branch. > */ > struct perf_branch_stack { > + bool user_callstack; > __u64 nr; > struct perf_branch_entry entries[0]; > }; > -- > 1.8.4.2 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/