From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753310AbbGVXUg (ORCPT ); Wed, 22 Jul 2015 19:20:36 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:54046 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbbGVXUd (ORCPT ); Wed, 22 Jul 2015 19:20:33 -0400 X-Helo: d03dlp03.boulder.ibm.com X-MailFrom: sukadev@linux.vnet.ibm.com X-RcptTo: sparclinux@vger.kernel.org Date: Wed, 22 Jul 2015 16:19:16 -0700 From: Sukadev Bhattiprolu To: Peter Zijlstra Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Michael Ellerman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org Subject: Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface Message-ID: <20150722231916.GA1863@us.ibm.com> References: <1436929315-28520-1-git-send-email-sukadev@linux.vnet.ibm.com> <1436929315-28520-8-git-send-email-sukadev@linux.vnet.ibm.com> <20150716222015.GO3644@twins.programming.kicks-ass.net> <20150722015045.GA24420@us.ibm.com> <20150722055503.GO25159@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150722055503.GO25159@twins.programming.kicks-ass.net> X-Operating-System: Linux 2.0.32 on an i486 User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15072223-0021-0000-0000-00000EA0A23C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra [peterz@infradead.org] wrote: | I've not woken up yet, and not actually fully read the email, but can | you stuff the entire above chunk inside the IPI? | | I think you could then actually optimize __perf_event_read() as well, | because all these events should be on the same context, so no point in | calling update_*time*() for every event or so. | Do you mean something like this (will move the rename to a separate patch before posting): -- >>From e8eddb5d3877ebdb3b71213a00aaa980f4010dd0 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Tue, 7 Jul 2015 21:45:23 -0400 Subject: [PATCH 1/1] perf: Define PMU_TXN_READ interface Define a new PERF_PMU_TXN_READ interface to read a group of counters at once. Note that we use this interface with all PMUs. PMUs that implement this interface use the ->read() operation to _queue_ the counters to be read and use ->commit_txn() to actually read all the queued counters at once. PMUs that don't implement PERF_PMU_TXN_READ ignore ->start_txn() and ->commit_txn() and continue to read counters one at a time. Thanks to input from Peter Zijlstra. Signed-off-by: Sukadev Bhattiprolu --- Changelog[v5] [Peter Zijlstra] Ensure the entire transaction happens on the same CPU. Changelog[v4] [Peter Zijlstra] Add lockdep_assert_held() in perf_event_read_group() --- include/linux/perf_event.h | 1 + kernel/events/core.c | 72 +++++++++++++++++++++++++++++++++++++------- 2 files changed, 62 insertions(+), 11 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 44bf05f..da307ad 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -169,6 +169,7 @@ struct perf_event; #define PERF_EVENT_TXN 0x1 #define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */ +#define PERF_PMU_TXN_READ 0x2 /* txn to read event group from PMU */ /** * pmu::capabilities flags diff --git a/kernel/events/core.c b/kernel/events/core.c index a6bd09d..7177dd8 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3174,12 +3174,8 @@ void perf_event_exec(void) rcu_read_unlock(); } -/* - * Cross CPU call to read the hardware event - */ -static void __perf_event_read(void *info) +static void __perf_event_read(struct perf_event *event, int update_ctx) { - struct perf_event *event = info; struct perf_event_context *ctx = event->ctx; struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); @@ -3194,7 +3190,7 @@ static void __perf_event_read(void *info) return; raw_spin_lock(&ctx->lock); - if (ctx->is_active) { + if (ctx->is_active && update_ctx) { update_context_time(ctx); update_cgrp_time_from_event(event); } @@ -3204,6 +3200,16 @@ static void __perf_event_read(void *info) raw_spin_unlock(&ctx->lock); } +/* + * Cross CPU call to read the hardware event + */ +static void __perf_event_read_ipi(void *info) +{ + struct perf_event *event = info; + + __perf_event_read(event, 1); +} + static inline u64 perf_event_count(struct perf_event *event) { if (event->pmu->count) @@ -3220,7 +3226,7 @@ static void perf_event_read(struct perf_event *event) */ if (event->state == PERF_EVENT_STATE_ACTIVE) { smp_call_function_single(event->oncpu, - __perf_event_read, event, 1); + __perf_event_read_ipi, event, 1); } else if (event->state == PERF_EVENT_STATE_INACTIVE) { struct perf_event_context *ctx = event->ctx; unsigned long flags; @@ -3765,6 +3771,36 @@ static void orphans_remove_work(struct work_struct *work) put_ctx(ctx); } +/* + * Use the transaction interface to read the group of events in @leader. + * PMUs like the 24x7 counters in Power, can use this to queue the events + * in the ->read() operation and perform the actual read in ->commit_txn. + * + * Other PMUs can ignore the ->start_txn and ->commit_txn and read each + * PMU directly in the ->read() operation. + */ +static int perf_event_read_group(struct perf_event *leader) +{ + int ret; + struct perf_event *sub; + struct pmu *pmu; + struct perf_event_context *ctx = leader->ctx; + + lockdep_assert_held(&ctx->mutex); + + pmu = leader->pmu; + + pmu->start_txn(pmu, PERF_PMU_TXN_READ); + + __perf_event_read(leader, 1); + list_for_each_entry(sub, &leader->sibling_list, group_entry) + __perf_event_read(sub, 0); + + ret = pmu->commit_txn(pmu); + + return ret; +} + u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) { u64 total = 0; @@ -3794,7 +3830,17 @@ static int perf_read_group(struct perf_event *event, lockdep_assert_held(&ctx->mutex); - count = perf_event_read_value(leader, &enabled, &running); + mutex_lock(&leader->child_mutex); + + ret = perf_event_read_group(leader); + if (ret) { + mutex_unlock(&leader->child_mutex); + return ret; + } + + count = perf_event_aggregate(leader, &enabled, &running); + + mutex_unlock(&leader->child_mutex); values[n++] = 1 + leader->nr_siblings; if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) @@ -3815,15 +3861,19 @@ static int perf_read_group(struct perf_event *event, list_for_each_entry(sub, &leader->sibling_list, group_entry) { n = 0; - values[n++] = perf_event_read_value(sub, &enabled, &running); + mutex_lock(&sub->child_mutex); + + values[n++] = perf_event_aggregate(sub, &enabled, &running); + + mutex_unlock(&sub->child_mutex); + if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(sub); size = n * sizeof(u64); - if (copy_to_user(buf + ret, values, size)) { + if (copy_to_user(buf + ret, values, size)) return -EFAULT; - } ret += size; } -- 1.7.9.5