Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754424AbaBFPuU (ORCPT ); Thu, 6 Feb 2014 10:50:20 -0500 Received: from mail-oa0-f48.google.com ([209.85.219.48]:33067 "EHLO mail-oa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894AbaBFPuS (ORCPT ); Thu, 6 Feb 2014 10:50:18 -0500 MIME-Version: 1.0 In-Reply-To: <1388728091-18564-14-git-send-email-zheng.z.yan@intel.com> References: <1388728091-18564-1-git-send-email-zheng.z.yan@intel.com> <1388728091-18564-14-git-send-email-zheng.z.yan@intel.com> Date: Thu, 6 Feb 2014 16:50:17 +0100 Message-ID: Subject: Re: [PATCH 13/14] perf, x86: enable LBR callstack when recording 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: > Try enabling the LBR callstack facility if user requests recording > user space callchain. Also adds a cpu pmu attribute to enable/disable > this feature. This feature is disabled by default because it may > contend for the LBR with other events that explicitly require branch > stack > We have discussed this patch before. I think you need to describe cleary what's going on based on priv levels. excl_user=0, excl_kernel=0 : user callstack via LBR, kernel via framepointer? excl_user=0, excl_kernel=1 : user callstack via LBR excl_user=1, excl_kernel=0 : kernel via framepointer? excl_user=1, excl_kernel=1 : nothing This does not come out clear from the code below. > Signed-off-by: Yan, Zheng > --- > arch/x86/kernel/cpu/perf_event.c | 99 ++++++++++++++++++++++++++++------------ > arch/x86/kernel/cpu/perf_event.h | 7 +++ > 2 files changed, 77 insertions(+), 29 deletions(-) > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 1509340..3ea184a 100644 > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -399,37 +399,49 @@ int x86_pmu_hw_config(struct perf_event *event) > > if (event->attr.precise_ip > precise) > return -EOPNOTSUPP; > + } > + /* > + * check that PEBS LBR correction does not conflict with > + * whatever the user is asking with attr->branch_sample_type > + */ > + if (event->attr.precise_ip > 1 && x86_pmu.intel_cap.pebs_format < 2) { > + u64 *br_type = &event->attr.branch_sample_type; > + > + if (has_branch_stack(event)) { > + if (!precise_br_compat(event)) > + return -EOPNOTSUPP; > + > + /* branch_sample_type is compatible */ > + > + } else { > + /* > + * user did not specify branch_sample_type > + * > + * For PEBS fixups, we capture all > + * the branches at the priv level of the > + * event. > + */ > + *br_type = PERF_SAMPLE_BRANCH_ANY; > + > + if (!event->attr.exclude_user) > + *br_type |= PERF_SAMPLE_BRANCH_USER; > + > + if (!event->attr.exclude_kernel) > + *br_type |= PERF_SAMPLE_BRANCH_KERNEL; > + } > + } else if ((event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) && > + !has_branch_stack(event) && > + x86_pmu.attr_lbr_callstack && > + !event->attr.exclude_user && > + (event->attach_state & PERF_ATTACH_TASK)) { > /* > - * check that PEBS LBR correction does not conflict with > - * whatever the user is asking with attr->branch_sample_type > + * user did not specify branch_sample_type, > + * try using the LBR call stack facility to > + * record call chains of user program. > */ > - if (event->attr.precise_ip > 1 && > - x86_pmu.intel_cap.pebs_format < 2) { > - u64 *br_type = &event->attr.branch_sample_type; > - > - if (has_branch_stack(event)) { > - if (!precise_br_compat(event)) > - return -EOPNOTSUPP; > - > - /* branch_sample_type is compatible */ > - > - } else { > - /* > - * user did not specify branch_sample_type > - * > - * For PEBS fixups, we capture all > - * the branches at the priv level of the > - * event. > - */ > - *br_type = PERF_SAMPLE_BRANCH_ANY; > - > - if (!event->attr.exclude_user) > - *br_type |= PERF_SAMPLE_BRANCH_USER; > - > - if (!event->attr.exclude_kernel) > - *br_type |= PERF_SAMPLE_BRANCH_KERNEL; > - } > - } > + event->attr.branch_sample_type = > + PERF_SAMPLE_BRANCH_USER | > + PERF_SAMPLE_BRANCH_CALL_STACK; > } > > /* > @@ -1828,10 +1840,39 @@ static ssize_t set_attr_rdpmc(struct device *cdev, > return count; > } > > +static ssize_t get_attr_lbr_callstack(struct device *cdev, > + struct device_attribute *attr, char *buf) > +{ > + return snprintf(buf, 40, "%d\n", x86_pmu.attr_lbr_callstack); > +} > + > +static ssize_t set_attr_lbr_callstack(struct device *cdev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + unsigned long val; > + ssize_t ret; > + > + ret = kstrtoul(buf, 0, &val); > + if (ret) > + return ret; > + > + if (!!val != !!x86_pmu.attr_lbr_callstack) { > + if (val && !x86_pmu_has_lbr_callstack()) > + return -EOPNOTSUPP; > + x86_pmu.attr_lbr_callstack = !!val; > + } > + return count; > +} > + > static DEVICE_ATTR(rdpmc, S_IRUSR | S_IWUSR, get_attr_rdpmc, set_attr_rdpmc); > +static DEVICE_ATTR(lbr_callstack, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH, > + get_attr_lbr_callstack, set_attr_lbr_callstack); > + > > static struct attribute *x86_pmu_attrs[] = { > &dev_attr_rdpmc.attr, > + &dev_attr_lbr_callstack.attr, > NULL, > }; > > diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h > index 3ed9629..b45258c 100644 > --- a/arch/x86/kernel/cpu/perf_event.h > +++ b/arch/x86/kernel/cpu/perf_event.h > @@ -400,6 +400,7 @@ struct x86_pmu { > * sysfs attrs > */ > int attr_rdpmc; > + int attr_lbr_callstack; > struct attribute **format_attrs; > struct attribute **event_attrs; > > @@ -504,6 +505,12 @@ static struct perf_pmu_events_attr event_attr_##v = { \ > > extern struct x86_pmu x86_pmu __read_mostly; > > +static inline bool x86_pmu_has_lbr_callstack(void) > +{ > + return x86_pmu.lbr_sel_map && > + x86_pmu.lbr_sel_map[PERF_SAMPLE_BRANCH_CALL_STACK_SHIFT] > 0; > +} > + > DECLARE_PER_CPU(struct cpu_hw_events, cpu_hw_events); > > int x86_perf_event_set_period(struct perf_event *event); > -- > 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/