From patchwork Fri Nov 18 19:01:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Namhyung Kim X-Patchwork-Id: 13048630 X-Patchwork-Delegate: bpf@iogearbox.net 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 D4F6EC433FE for ; Fri, 18 Nov 2022 19:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242876AbiKRTBY (ORCPT ); Fri, 18 Nov 2022 14:01:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241915AbiKRTBN (ORCPT ); Fri, 18 Nov 2022 14:01:13 -0500 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91DF1218A5; Fri, 18 Nov 2022 11:01:12 -0800 (PST) Received: by mail-pj1-x102e.google.com with SMTP id d13-20020a17090a3b0d00b00213519dfe4aso5908211pjc.2; Fri, 18 Nov 2022 11:01:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:from:to:cc:subject:date:message-id:reply-to; bh=PZG45DVCWzpKQix+00S+7v15lsLikdvOFa2L1rhz02E=; b=gu7/79lwAamCIznCAQOwdlvYS7qrs2p/YrBB243/Ap0J8W/HADwP6LTpsB8hFKoLh+ ge7dnsjdlbJI0kdiTd20UCBBzR0rG/bmaGSwAhDqNgnPEf2BDcUn80RYU4yfwqjf6Lsn QVA4iU5mBQfR4caKjOteYZPm5WmSxTy3C1/Zmnrqb4UiWWk2TxyRq+Yo5QKn4YtHAwOe tXrU1RNPj9C2OcWynkhuiF1gQuMGasn26mZntKlbo2b+lPsMzuXgpCCkMQs72A1oFlNy QJiGeQZzKJt8OFNXdNVQWDi0CXXAGIKPNgLq/uRPs6OxeFWHN97tCwV2FvX4Aq4RZQ0B 5ZRQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=PZG45DVCWzpKQix+00S+7v15lsLikdvOFa2L1rhz02E=; b=kgX1RQme290bgJwA3iXrt89xS0/4Eh8Jp0whF/hDUWfHoU2RxDccn44pLS/Nxf1L5A 1YYoWdG00wOI2YzvMuu0bsDq0aleWzc1+4s8Zkf3HIOKZuAxz8fblHki6Gub94cv8dh+ QfQ8Ij+CuJ8aqGGsfgZxyu2sy6hmD+4s0hJo6FkyIDIYFYy+I+5DG5v9kgDxC5OW5ygj aGFFXB2Qk1bVHv30uErZIZELs2Hna+GwYDbufmj8pkryNjt6HJlObGzr7MqPmawubZDJ 3dhcZR6z16abZQjrhOc0YEZthwzdALUQIXQnw5DHGxsrmNTcmOJ5DHatm4Sb2SRgtADu Rmxw== X-Gm-Message-State: ANoB5pktsEx5oLU3WmCmEorKm4uROs3olmelCRJa6r63HrUE7vTNelRJ VCijOVkExvuzvZ0dfdvqY40= X-Google-Smtp-Source: AA0mqf4Bztezj9f2y+2p36BvF+DYXQt+bd7bC5bjYeng8ebyzS+a7af+Bvpia1V807T5PIDNuhWpYg== X-Received: by 2002:a17:903:2112:b0:188:7dca:6f41 with SMTP id o18-20020a170903211200b001887dca6f41mr838705ple.72.1668798071806; Fri, 18 Nov 2022 11:01:11 -0800 (PST) Received: from balhae.corp.google.com ([2620:15c:2c1:200:2f31:8015:7312:9278]) by smtp.gmail.com with ESMTPSA id g11-20020a17090a67cb00b0021282014066sm5750994pjm.9.2022.11.18.11.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Nov 2022 11:01:11 -0800 (PST) Sender: Namhyung Kim From: Namhyung Kim To: Arnaldo Carvalho de Melo , Jiri Olsa Cc: Ingo Molnar , Peter Zijlstra , LKML , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, Song Liu , bpf@vger.kernel.org, Blake Jones , Chris Li Subject: [PATCH] perf lock contention: Do not use BPF task local storage Date: Fri, 18 Nov 2022 11:01:09 -0800 Message-Id: <20221118190109.1512674-1-namhyung@kernel.org> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org It caused some troubles when a lock inside kmalloc is contended because task local storage would allocate memory using kmalloc. It'd create a recusion and even crash in my system. There could be a couple of workarounds but I think the simplest one is to use a pre-allocated hash map. We could fix the task local storage to use the safe BPF allocator, but it takes time so let's change this until it happens actually. Signed-off-by: Namhyung Kim Acked-by: Martin KaFai Lau --- tools/perf/util/bpf_lock_contention.c | 1 + .../perf/util/bpf_skel/lock_contention.bpf.c | 34 ++++++++++++------- 2 files changed, 23 insertions(+), 12 deletions(-) diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c index 0deec1178778..4db9ad3d50c4 100644 --- a/tools/perf/util/bpf_lock_contention.c +++ b/tools/perf/util/bpf_lock_contention.c @@ -39,6 +39,7 @@ int lock_contention_prepare(struct lock_contention *con) bpf_map__set_value_size(skel->maps.stacks, con->max_stack * sizeof(u64)); bpf_map__set_max_entries(skel->maps.stacks, con->map_nr_entries); bpf_map__set_max_entries(skel->maps.lock_stat, con->map_nr_entries); + bpf_map__set_max_entries(skel->maps.tstamp, con->map_nr_entries); if (target__has_cpu(target)) ncpus = perf_cpu_map__nr(evlist->core.user_requested_cpus); diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 1bb8628e7c9f..9681cb59b0df 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -40,10 +40,10 @@ struct { /* maintain timestamp at the beginning of contention */ struct { - __uint(type, BPF_MAP_TYPE_TASK_STORAGE); - __uint(map_flags, BPF_F_NO_PREALLOC); + __uint(type, BPF_MAP_TYPE_HASH); __type(key, int); __type(value, struct tstamp_data); + __uint(max_entries, MAX_ENTRIES); } tstamp SEC(".maps"); /* actual lock contention statistics */ @@ -103,18 +103,28 @@ static inline int can_record(void) SEC("tp_btf/contention_begin") int contention_begin(u64 *ctx) { - struct task_struct *curr; + __u32 pid; struct tstamp_data *pelem; if (!enabled || !can_record()) return 0; - curr = bpf_get_current_task_btf(); - pelem = bpf_task_storage_get(&tstamp, curr, NULL, - BPF_LOCAL_STORAGE_GET_F_CREATE); - if (!pelem || pelem->lock) + pid = bpf_get_current_pid_tgid(); + pelem = bpf_map_lookup_elem(&tstamp, &pid); + if (pelem && pelem->lock) return 0; + if (pelem == NULL) { + struct tstamp_data zero = {}; + + bpf_map_update_elem(&tstamp, &pid, &zero, BPF_ANY); + pelem = bpf_map_lookup_elem(&tstamp, &pid); + if (pelem == NULL) { + lost++; + return 0; + } + } + pelem->timestamp = bpf_ktime_get_ns(); pelem->lock = (__u64)ctx[0]; pelem->flags = (__u32)ctx[1]; @@ -128,7 +138,7 @@ int contention_begin(u64 *ctx) SEC("tp_btf/contention_end") int contention_end(u64 *ctx) { - struct task_struct *curr; + __u32 pid; struct tstamp_data *pelem; struct contention_key key; struct contention_data *data; @@ -137,8 +147,8 @@ int contention_end(u64 *ctx) if (!enabled) return 0; - curr = bpf_get_current_task_btf(); - pelem = bpf_task_storage_get(&tstamp, curr, NULL, 0); + pid = bpf_get_current_pid_tgid(); + pelem = bpf_map_lookup_elem(&tstamp, &pid); if (!pelem || pelem->lock != ctx[0]) return 0; @@ -156,7 +166,7 @@ int contention_end(u64 *ctx) }; bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST); - pelem->lock = 0; + bpf_map_delete_elem(&tstamp, &pid); return 0; } @@ -169,7 +179,7 @@ int contention_end(u64 *ctx) if (data->min_time > duration) data->min_time = duration; - pelem->lock = 0; + bpf_map_delete_elem(&tstamp, &pid); return 0; }