From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09D67C433F5 for ; Thu, 9 Dec 2021 11:35:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236828AbhLILif (ORCPT ); Thu, 9 Dec 2021 06:38:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236782AbhLILid (ORCPT ); Thu, 9 Dec 2021 06:38:33 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D724C061746 for ; Thu, 9 Dec 2021 03:35:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=zCopsbGKBV9BpPlCXS61pCDV3DmBNf3UasJSV1vCB6A=; b=OUFSQqAb1EVecmS1bPeJjT9Jev ZWRdfaKs1RPKr8yoifIVeTf6Ht9PMm/xc2Qzs1p5G5KzSy4kTxqTGuhNDZ6XRWy4BZIRvfxaAiMzt Y2YZv9q52w+4PSJqHiPt/7su6Lkm+ua96LNQE027U42n5CP3GrW+bQJt2j9I3jLEYocxm166fSYEJ rSiYfVPv838zxm4d/03/PmgG+BmQvzPttWBYtbH6JVWt+ZQgVS29Pue0Jixa8rq7XINTZfTOR+lag iFswr4J8yDVADYiqZTyB6DYOK1HUGo/O6Jaktg958Gc6MfQi8ZPNN05CpAP/aD+A0/JOa+qhez5DY SjlQWmzg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mvHhI-009Iaf-3M; Thu, 09 Dec 2021 11:34:48 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6B895300079; Thu, 9 Dec 2021 12:34:48 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3F9982BB95D96; Thu, 9 Dec 2021 12:34:48 +0100 (CET) Date: Thu, 9 Dec 2021 12:34:48 +0100 From: Peter Zijlstra To: Namhyung Kim Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Mark Rutland , Alexander Shishkin , LKML , Stephane Eranian , Andi Kleen , Ian Rogers , Song Liu Subject: Re: [PATCH v3] perf/core: Set event shadow time for inactive events too Message-ID: References: <20211205224843.1503081-1-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 09, 2021 at 12:26:32PM +0100, Peter Zijlstra wrote: > On Sun, Dec 05, 2021 at 02:48:43PM -0800, Namhyung Kim wrote: > > > Actually 18446744069443110306 is 0xffffffff01b345a2 so it seems to > > have a negative enabled time. In fact, bperf keeps values returned by > > bpf_perf_event_read_value() which calls perf_event_read_local(), and > > accumulates delta between two calls. When event->shadow_ctx_time is > > not set, it'd return invalid enabled time which is bigger than normal. > > *that*, how does it happen that shadow_time isn't set? It should be last > set when the event switches to INACTIVE, no? At which point the logic in > perf_event_read_local() should make @enabled move forward while @running > stays put. > > Let me go rummage around a bit... either I'm missing something obvious > or something's smelly. How's this then? diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 7b7525e9155f..82baa8bdfc86 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -686,9 +686,7 @@ struct perf_event { /* * timestamp shadows the actual context timing but it can * be safely used in NMI interrupt context. It reflects the - * context time as it was when the event was last scheduled in, - * or when ctx_sched_in failed to schedule the event because we - * run out of PMC. + * context time as it was when the event was last scheduled in. * * ctx_time already accounts for ctx->timestamp. Therefore to * compute ctx_time for a sample, simply add perf_clock(). diff --git a/kernel/events/core.c b/kernel/events/core.c index 28aaeacdaea1..20637b7f420c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -640,6 +640,9 @@ __perf_update_times(struct perf_event *event, u64 now, u64 *enabled, u64 *runnin *running += delta; } +static void perf_set_shadow_time(struct perf_event *event, + struct perf_event_context *ctx); + static void perf_event_update_time(struct perf_event *event) { u64 now = perf_event_time(event); @@ -647,6 +650,7 @@ static void perf_event_update_time(struct perf_event *event) __perf_update_times(event, now, &event->total_time_enabled, &event->total_time_running); event->tstamp = now; + perf_set_shadow_time(event, event->ctx); } static void perf_event_update_sibling_time(struct perf_event *leader) @@ -2552,8 +2556,6 @@ event_sched_in(struct perf_event *event, perf_pmu_disable(event->pmu); - perf_set_shadow_time(event, ctx); - perf_log_itrace_start(event); if (event->pmu->add(event, PERF_EF_START)) { @@ -3707,29 +3709,6 @@ static noinline int visit_groups_merge(struct perf_cpu_context *cpuctx, return 0; } -static inline bool event_update_userpage(struct perf_event *event) -{ - if (likely(!atomic_read(&event->mmap_count))) - return false; - - perf_event_update_time(event); - perf_set_shadow_time(event, event->ctx); - perf_event_update_userpage(event); - - return true; -} - -static inline void group_update_userpage(struct perf_event *group_event) -{ - struct perf_event *event; - - if (!event_update_userpage(group_event)) - return; - - for_each_sibling_event(event, group_event) - event_update_userpage(event); -} - static int merge_sched_in(struct perf_event *event, void *data) { struct perf_event_context *ctx = event->ctx; @@ -3748,15 +3727,14 @@ static int merge_sched_in(struct perf_event *event, void *data) } if (event->state == PERF_EVENT_STATE_INACTIVE) { - *can_add_hw = 0; if (event->attr.pinned) { perf_cgroup_event_disable(event, ctx); perf_event_set_state(event, PERF_EVENT_STATE_ERROR); - } else { - ctx->rotate_necessary = 1; - perf_mux_hrtimer_restart(cpuctx); - group_update_userpage(event); } + + *can_add_hw = 0; + ctx->rotate_necessary = 1; + perf_mux_hrtimer_restart(cpuctx); } return 0; @@ -6349,7 +6327,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) ring_buffer_attach(event, rb); perf_event_update_time(event); - perf_set_shadow_time(event, event->ctx); perf_event_init_userpage(event); perf_event_update_userpage(event); } else {