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 C3854CCA479 for ; Mon, 4 Jul 2022 15:06:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234868AbiGDPGp (ORCPT ); Mon, 4 Jul 2022 11:06:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234943AbiGDPGc (ORCPT ); Mon, 4 Jul 2022 11:06:32 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 651D11181E for ; Mon, 4 Jul 2022 08:06:18 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id y4-20020a25b9c4000000b0066e573fb0fcso1173602ybj.21 for ; Mon, 04 Jul 2022 08:06:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=V6/7gBssT9f8qylfI12t9/BYdohkMdKIWfeQweBYfic=; b=JoVGDf6yQ8hGirou83feMsM4fL6UwLihSOqkkLWWVbbLtWhghXfhWuyGi7Gb7aA4KC HT6QhfDG1/w3eMQbfxFGGy0lV0o65w9EQxD/Zup+jg6IzZx0IB6ouZLD0PgjF8tUc9p5 JYwZTgOkQ+VR3vTmGIGyuk6MDYpfVw8MWyDx256153/zJCXt6uETyGdn43Tn3YoeVDqc terWTuZUxZKccqKMfObUL1ySacZIWbCEizjsXbCXgIRgsrIXLZRiaddpXxsVs8zsCiVs fVrPnCz03zW3qC+vf6NAp0pen31JzqIP3Dlf1koXr99dwWadbrUjqQ6JWirJ30JZvM/4 k4Ig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=V6/7gBssT9f8qylfI12t9/BYdohkMdKIWfeQweBYfic=; b=wRjWPn5ur7rutHEWJvtB4WozW61QiBJwTjyV+0Es3uoFLMDvPGa9SDN3d6Lgkp0JUR jUPHhQ2AGUkFe8M5ar4e/z+d1Lr6a0EwIBVUJJTcw+krBHspIt8VKFmtw9Wmefna8Af+ 4EYUB8LSPCVCqH0SlgnhUrjXh/889o7NlRw+5k4Xq3h3xVJs7F4u3d5vjTlHB7mweAx8 SVzdcRYCYEFqOWNEecxc/B//aNQo12sxDZ0sKATGjM3FWhXHYxX7EmDDUIww5JALbJ68 ILF4zu2F+olHlgSRZ7cz9O2MqLIzjSC2gcrdKiWW89NP9uYDcl5MoklvIhViAIA5pnaV iupw== X-Gm-Message-State: AJIora+X+udWWpgBImDu2AqX5g9Vn1btv3Xr5rYHpG30ANlPjFzwEUwo JAcwqD0MUtm1jAFIeF8+4ylR/NExZg== X-Google-Smtp-Source: AGRyM1tBjV0pVOkHHvxY5ShCb3zsNgcpQYjMGcRVbXSuG4UWDvuTzPmMgrbvjsm2+aO9XSs5DSKPcBWbQA== X-Received: from elver.muc.corp.google.com ([2a00:79e0:9c:201:6edf:e1bc:9a92:4ad0]) (user=elver job=sendgmr) by 2002:a81:11c7:0:b0:31c:8c85:c4be with SMTP id 190-20020a8111c7000000b0031c8c85c4bemr8356031ywr.235.1656947177651; Mon, 04 Jul 2022 08:06:17 -0700 (PDT) Date: Mon, 4 Jul 2022 17:05:08 +0200 In-Reply-To: <20220704150514.48816-1-elver@google.com> Message-Id: <20220704150514.48816-9-elver@google.com> Mime-Version: 1.0 References: <20220704150514.48816-1-elver@google.com> X-Mailer: git-send-email 2.37.0.rc0.161.g10f37bed90-goog Subject: [PATCH v3 08/14] perf/hw_breakpoint: Remove useless code related to flexible breakpoints From: Marco Elver To: elver@google.com, Peter Zijlstra , Frederic Weisbecker , Ingo Molnar Cc: Thomas Gleixner , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Dmitry Vyukov , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org, x86@kernel.org, linux-sh@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org Flexible breakpoints have never been implemented, with bp_cpuinfo::flexible always being 0. Unfortunately, they still occupy 4 bytes in each bp_cpuinfo and bp_busy_slots, as well as computing the max flexible count in fetch_bp_busy_slots(). This again causes suboptimal code generation, when we always know that `!!slots.flexible` will be 0. Just get rid of the flexible "placeholder" and remove all real code related to it. Make a note in the comment related to the constraints algorithm but don't remove them from the algorithm, so that if in future flexible breakpoints need supporting, it should be trivial to revive them (along with reverting this change). Signed-off-by: Marco Elver Reviewed-by: Dmitry Vyukov --- v2: * Also remove struct bp_busy_slots, and simplify functions. --- kernel/events/hw_breakpoint.c | 57 +++++++++++------------------------ 1 file changed, 17 insertions(+), 40 deletions(-) diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index 9c9bf17666a5..8b40fca1a063 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -45,8 +45,6 @@ struct bp_cpuinfo { #else unsigned int *tsk_pinned; #endif - /* Number of non-pinned cpu/task breakpoints in a cpu */ - unsigned int flexible; /* XXX: placeholder, see fetch_this_slot() */ }; static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]); @@ -67,12 +65,6 @@ static const struct rhashtable_params task_bps_ht_params = { static bool constraints_initialized __ro_after_init; -/* Gather the number of total pinned and un-pinned bp in a cpuset */ -struct bp_busy_slots { - unsigned int pinned; - unsigned int flexible; -}; - /* Serialize accesses to the above constraints */ static DEFINE_MUTEX(nr_bp_mutex); @@ -190,14 +182,14 @@ static const struct cpumask *cpumask_of_bp(struct perf_event *bp) } /* - * Report the number of pinned/un-pinned breakpoints we have in - * a given cpu (cpu > -1) or in all of them (cpu = -1). + * Returns the max pinned breakpoint slots in a given + * CPU (cpu > -1) or across all of them (cpu = -1). */ -static void -fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp, - enum bp_type_idx type) +static int +max_bp_pinned_slots(struct perf_event *bp, enum bp_type_idx type) { const struct cpumask *cpumask = cpumask_of_bp(bp); + int pinned_slots = 0; int cpu; for_each_cpu(cpu, cpumask) { @@ -210,24 +202,10 @@ fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp, else nr += task_bp_pinned(cpu, bp, type); - if (nr > slots->pinned) - slots->pinned = nr; - - nr = info->flexible; - if (nr > slots->flexible) - slots->flexible = nr; + pinned_slots = max(nr, pinned_slots); } -} -/* - * For now, continue to consider flexible as pinned, until we can - * ensure no flexible event can ever be scheduled before a pinned event - * in a same cpu. - */ -static void -fetch_this_slot(struct bp_busy_slots *slots, int weight) -{ - slots->pinned += weight; + return pinned_slots; } /* @@ -298,7 +276,12 @@ __weak void arch_unregister_hw_breakpoint(struct perf_event *bp) } /* - * Constraints to check before allowing this new breakpoint counter: + * Constraints to check before allowing this new breakpoint counter. + * + * Note: Flexible breakpoints are currently unimplemented, but outlined in the + * below algorithm for completeness. The implementation treats flexible as + * pinned due to no guarantee that we currently always schedule flexible events + * before a pinned event in a same CPU. * * == Non-pinned counter == (Considered as pinned for now) * @@ -340,8 +323,8 @@ __weak void arch_unregister_hw_breakpoint(struct perf_event *bp) */ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type) { - struct bp_busy_slots slots = {0}; enum bp_type_idx type; + int max_pinned_slots; int weight; int ret; @@ -357,15 +340,9 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type) type = find_slot_idx(bp_type); weight = hw_breakpoint_weight(bp); - fetch_bp_busy_slots(&slots, bp, type); - /* - * Simulate the addition of this breakpoint to the constraints - * and see the result. - */ - fetch_this_slot(&slots, weight); - - /* Flexible counters need to keep at least one slot */ - if (slots.pinned + (!!slots.flexible) > hw_breakpoint_slots_cached(type)) + /* Check if this new breakpoint can be satisfied across all CPUs. */ + max_pinned_slots = max_bp_pinned_slots(bp, type) + weight; + if (max_pinned_slots > hw_breakpoint_slots_cached(type)) return -ENOSPC; ret = arch_reserve_bp_slot(bp); -- 2.37.0.rc0.161.g10f37bed90-goog