Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752456Ab3FZJAv (ORCPT ); Wed, 26 Jun 2013 05:00:51 -0400 Received: from mail-ob0-f170.google.com ([209.85.214.170]:45962 "EHLO mail-ob0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752004Ab3FZJAr (ORCPT ); Wed, 26 Jun 2013 05:00:47 -0400 MIME-Version: 1.0 In-Reply-To: <1372150039-15151-7-git-send-email-zheng.z.yan@intel.com> References: <1372150039-15151-1-git-send-email-zheng.z.yan@intel.com> <1372150039-15151-7-git-send-email-zheng.z.yan@intel.com> Date: Wed, 26 Jun 2013 11:00:46 +0200 Message-ID: Subject: Re: [PATCH 6/7] perf, x86: Use LBR call stack to get user callchain From: Stephane Eranian To: "Yan, Zheng" Cc: LKML , Ingo Molnar , Peter Zijlstra , 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 Content-Length: 16308 Lines: 407 On Tue, Jun 25, 2013 at 10:47 AM, Yan, Zheng wrote: > From: "Yan, Zheng" > > Try enabling the LBR call stack feature if event request recording > callchain. Try utilizing the LBR call stack to get user callchain > in case of there is no frame pointer. > > This patch also adds a cpu pmu attribute to enable/disable this > feature. > > Signed-off-by: Yan, Zheng > --- > arch/x86/kernel/cpu/perf_event.c | 128 +++++++++++++++++++++-------- > arch/x86/kernel/cpu/perf_event.h | 7 ++ > arch/x86/kernel/cpu/perf_event_intel.c | 20 ++--- > arch/x86/kernel/cpu/perf_event_intel_lbr.c | 3 + > include/linux/perf_event.h | 6 ++ > kernel/events/core.c | 11 ++- > 6 files changed, 126 insertions(+), 49 deletions(-) > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 639aa4d..a07eb03 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; > } > > /* > @@ -1825,10 +1837,34 @@ 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 = simple_strtoul(buf, NULL, 0); > + > + if (x86_pmu.attr_lbr_callstack != !!val) { > + 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, > + get_attr_lbr_callstack, set_attr_lbr_callstack); > + > Given the known limitations, I think it would be good for users to be allowed to probe the current setting of lbr_callstack. $ cat /sys/devices/cpu/lbr_callstack cat: /sys/devices/cpu/lbr_callstack: Permission denied > static struct attribute *x86_pmu_attrs[] = { > &dev_attr_rdpmc.attr, > + &dev_attr_lbr_callstack.attr, > NULL, > }; > > @@ -1955,12 +1991,29 @@ 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 && > + x86_pmu.attr_lbr_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; > @@ -1989,11 +2042,16 @@ 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; > } > @@ -2023,12 +2081,12 @@ 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)); > @@ -2041,6 +2099,10 @@ 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.h b/arch/x86/kernel/cpu/perf_event.h > index 0116970..536470d 100644 > --- a/arch/x86/kernel/cpu/perf_event.h > +++ b/arch/x86/kernel/cpu/perf_event.h > @@ -390,6 +390,7 @@ struct x86_pmu { > * sysfs attrs > */ > int attr_rdpmc; > + int attr_lbr_callstack; > struct attribute **format_attrs; > struct attribute **event_attrs; > > @@ -496,6 +497,12 @@ 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); > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c > index f59b46e..baa8384 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel.c > +++ b/arch/x86/kernel/cpu/perf_event_intel.c > @@ -882,15 +882,10 @@ static __initconst const u64 atom_hw_cache_event_ids > }, > }; > > -static inline bool intel_pmu_needs_lbr_smpl(struct perf_event *event) > +static inline bool intel_pmu_needs_lbr_callstack(struct perf_event *event) > { > - /* user explicitly requested branch sampling */ > - if (has_branch_stack(event)) > - return true; > - > - /* implicit branch sampling to correct PEBS skid */ > - if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1 && > - x86_pmu.intel_cap.pebs_format < 2) > + if ((event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) && > + (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)) > return true; > > return false; > @@ -1054,7 +1049,7 @@ static void intel_pmu_disable_event(struct perf_event *event) > * must disable before any actual event > * because any event may be combined with LBR > */ > - if (intel_pmu_needs_lbr_smpl(event)) > + if (needs_branch_stack(event)) > intel_pmu_lbr_disable(event); > > if (unlikely(hwc->config_base == MSR_ARCH_PERFMON_FIXED_CTR_CTRL)) { > @@ -1115,7 +1110,7 @@ static void intel_pmu_enable_event(struct perf_event *event) > * must enabled before any actual event > * because any event may be combined with LBR > */ > - if (intel_pmu_needs_lbr_smpl(event)) > + if (needs_branch_stack(event)) > intel_pmu_lbr_enable(event); > > if (event->attr.exclude_host) > @@ -1237,7 +1232,8 @@ 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))) > data.br_stack = &cpuc->lbr_stack; > > if (perf_event_overflow(event, &data, regs)) > @@ -1568,7 +1564,7 @@ static int intel_pmu_hw_config(struct perf_event *event) > if (event->attr.precise_ip && x86_pmu.pebs_aliases) > x86_pmu.pebs_aliases(event); > > - if (intel_pmu_needs_lbr_smpl(event)) { > + if (needs_branch_stack(event)) { > ret = intel_pmu_setup_lbr_filter(event); > if (ret) > return ret; > diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c > index 43b16b4..3be2d7b 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c > +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c > @@ -709,6 +709,8 @@ 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; > @@ -861,6 +863,7 @@ void intel_pmu_lbr_init_hsw(void) > > x86_pmu.lbr_sel_mask = LBR_SEL_MASK; > x86_pmu.lbr_sel_map = hsw_lbr_sel_map; > + x86_pmu.attr_lbr_callstack = 1; > > pr_cont("16-deep LBR, "); > } > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index fa4c1bf..168e66e 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -97,6 +97,7 @@ struct perf_branch_entry { > * recent branch. > */ > struct perf_branch_stack { > + unsigned user_callstack:1; > __u64 nr; > struct perf_branch_entry entries[0]; > }; > @@ -759,6 +760,11 @@ static inline bool has_branch_stack(struct perf_event *event) > return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK; > } > > +static inline bool needs_branch_stack(struct perf_event *event) > +{ > + return event->attr.branch_sample_type != 0; > +} > + > extern int perf_output_begin(struct perf_output_handle *handle, > struct perf_event *event, unsigned int size); > extern void perf_output_end(struct perf_output_handle *handle); > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 4aad901..38eaa2b 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -1117,7 +1117,7 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx) > if (is_cgroup_event(event)) > ctx->nr_cgroups++; > > - if (has_branch_stack(event)) > + if (needs_branch_stack(event)) > ctx->nr_branch_stack++; > > list_add_rcu(&event->event_entry, &ctx->event_list); > @@ -1274,7 +1274,7 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) > cpuctx->cgrp = NULL; > } > > - if (has_branch_stack(event)) { > + if (needs_branch_stack(event)) { > if (ctx->is_active) > __get_cpu_var(perf_branch_stack_events)--; > ctx->nr_branch_stack--; > @@ -3155,7 +3155,7 @@ static void free_event(struct perf_event *event) > static_key_slow_dec_deferred(&perf_sched_events); > } > > - if (has_branch_stack(event)) > + if (needs_branch_stack(event)) > static_key_slow_dec_deferred(&perf_sched_events); > } > > @@ -6545,6 +6545,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, > if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP)) > goto done; > > + if (!has_branch_stack(event)) > + event->attr.branch_sample_type = 0; > + > pmu = perf_init_event(event); > > done: > @@ -6577,7 +6580,7 @@ done: > return ERR_PTR(err); > } > } > - if (has_branch_stack(event)) > + if (needs_branch_stack(event)) > static_key_slow_inc(&perf_sched_events.key); > } > > -- > 1.8.1.4 > -- 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/