From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753820AbcHQUz5 (ORCPT ); Wed, 17 Aug 2016 16:55:57 -0400 Received: from mail-pf0-f174.google.com ([209.85.192.174]:36652 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753564AbcHQUzf (ORCPT ); Wed, 17 Aug 2016 16:55:35 -0400 From: David Carrillo-Cisneros To: linux-kernel@vger.kernel.org Cc: "x86@kernel.org" , Ingo Molnar , Thomas Gleixner , Andi Kleen , Kan Liang , Peter Zijlstra , Vegard Nossum , Paul Turner , Stephane Eranian , David Carrillo-Cisneros Subject: [PATCH v3 3/4] perf/core: introduce PMU_EV_CAP_READ_ACTIVE_PKG Date: Wed, 17 Aug 2016 13:55:06 -0700 Message-Id: <1471467307-61171-4-git-send-email-davidcc@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1471467307-61171-1-git-send-email-davidcc@google.com> References: <1471467307-61171-1-git-send-email-davidcc@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce the flag PMU_EV_CAP_READ_ACTIVE_PKG, useful for uncore events, that allows a PMU to signal the generic perf code that an event is readable in the current CPU if the event is active in a CPU in the same package as the current CPU. This is an optimization that avoids a unnecessary IPI for the common case where uncore events are run and read in the same package but in different CPUs. As an example, the IPI removal speeds up perf_read in my Haswell system as follows: - For event UNC_C_LLC_LOOKUP: From 260 us to 31 us. - For event RAPL's power/energy-cores/: From to 255 us to 27 us. For the optimization to work, all events in the group must have it (similarly to PERF_EV_CAP_SOFTWARE). Signed-off-by: David Carrillo-Cisneros --- include/linux/perf_event.h | 3 +++ kernel/events/core.c | 25 +++++++++++++++++++++++-- 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 6f7459f..5c53625 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -514,8 +514,11 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *, * Event capabilities. For event_caps and groups caps. * * PERF_EV_CAP_SOFTWARE: Is a software event. + * PERF_EV_CAP_READ_ACTIVE_PKG: A CPU event (or cgroup event) that can be read + * from any CPU in the package where it is active. */ #define PERF_EV_CAP_SOFTWARE BIT(0) +#define PERF_EV_CAP_READ_ACTIVE_PKG BIT(1) #define SWEVENT_HLIST_BITS 8 #define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS) diff --git a/kernel/events/core.c b/kernel/events/core.c index 5b83509..06137bb 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3388,6 +3388,22 @@ struct perf_read_data { int ret; }; +static int find_cpu_to_read(struct perf_event *event, int local_cpu) +{ + int event_cpu = event->oncpu; + u16 local_pkg, event_pkg; + + if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) { + event_pkg = topology_physical_package_id(event_cpu); + local_pkg = topology_physical_package_id(local_cpu); + + if (event_pkg == local_pkg) + return local_cpu; + } + + return event_cpu; +} + /* * Cross CPU call to read the hardware event */ @@ -3509,7 +3525,7 @@ u64 perf_event_read_local(struct perf_event *event) static int perf_event_read(struct perf_event *event, bool group) { - int ret = 0; + int ret = 0, cpu_to_read, local_cpu; /* * If event is enabled and currently active on a CPU, update the @@ -3521,7 +3537,12 @@ static int perf_event_read(struct perf_event *event, bool group) .group = group, .ret = 0, }; - ret = smp_call_function_single(event->oncpu, + + local_cpu = get_cpu(); + cpu_to_read = find_cpu_to_read(event, local_cpu); + put_cpu(); + + ret = smp_call_function_single(cpu_to_read, __perf_event_read, &data, 1); /* event must have been read from an online CPU. */ WARN_ON_ONCE(ret); -- 2.8.0.rc3.226.g39d4020