From patchwork Mon Feb 24 18:42:49 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chun-Tse Shao X-Patchwork-Id: 13988805 Received: from mail-ot1-f74.google.com (mail-ot1-f74.google.com [209.85.210.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 41DC0264A76 for ; Mon, 24 Feb 2025 18:50:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740423030; cv=none; b=dH90RFzDC6LLb4smM/9m4OcIYxZD1w4xfg3VEX0STLZ0lYqaC6/kvl3ftIAzlp1m4XkvMJc38b/rZiR0y2RE5Vxkabrsf2mWFojPHFlyVzORQPxVKq6X5I2z8DorfeK85ar76yOvnCsKKxGeqUTi4fI+Cv6Yq2OywwDaX65epGc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740423030; c=relaxed/simple; bh=sX6k+ExVgGNyDnumdmJIdayUEA+By8ga08Ti0Wfuoc8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=dPuqxSNTylz+aMkZ9PRdNfzz2K7T1udf+rxrw3opCdgc4Nwf/DLq3XRLlTJXWzBWsvFzxYvDskSPyLgP/O27jtyL4p0jEsS4HyF2hW3jKcCxLBlHIfPbHcHhZEhPqAcZpao8YwszT94ii9WFP9cgqhksv0TboPsRpA6E9jYNRaI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--ctshao.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=HQd5SDJl; arc=none smtp.client-ip=209.85.210.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--ctshao.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="HQd5SDJl" Received: by mail-ot1-f74.google.com with SMTP id 46e09a7af769-7272fc9b9f8so1365871a34.2 for ; Mon, 24 Feb 2025 10:50:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740423027; x=1741027827; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=uT5qN4teqIhN8OgGcN83osIEOThqIeAxronJTF18w94=; b=HQd5SDJlfoj9fEmnTN3O/DrPD5/CwTXNx7y/8MBBaA4+Ap+Y4LrrCpCtGzdrRA2K1q +RoqQ9tL/tGbO+/U7glBf8xDxk1PR6psZf7wU+eTPm0Fjr8rAFJ9ZqS8Li9o5uVsa/bQ MSKMSmgr75wb6ygHy3kzDTVOdlpp9psPqT0mVCkPO8ceH7qDp3KUVNzPISdDomCLvIJy ULVP2eVIDM4eFLDaziNiK5aX0OwT4TG2MKRfEd8aZWSljV3Hb8gbYd3xQ9FwOb16v35K J5Kqcg7rhrRXVH20UI44GHEPEskXA67F68LHGSPm/MjOaAPgVhNd75hCW9KlqDbQMFeY xVOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740423027; x=1741027827; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=uT5qN4teqIhN8OgGcN83osIEOThqIeAxronJTF18w94=; b=Cmn5b8Xww722+5Ytk1u80nkqJTsUE0027krVDl0jbPF3lXBxG6/xv//UnA7XsvyfU7 QV+KSIVoLQTCothIc6d6+isAnxJpK4CZN13GeXqZMko5Lj7+2DU6rH+W6stiWQfSArXm psH1O0HIC8sLjSGb5wvhxqzhBGSZRHG0nOL4bwoRm3Hi0/D3r8oMJNv0WbOxyppBo4fi ELVeijkil65F6diVuuvRft8KD1PBWem8AYJ2EBWIcOns3fuivbQxyY2vIEQy6aoICSeJ eYTqh9CuyrHqMkkGhFnAb02vLsb/jG8l+6Ygjx0Y9zoijUNbGfEbNQdflJEPJAi2/mvN 22Xg== X-Forwarded-Encrypted: i=1; AJvYcCWAOMpX8JOjyjjRMZkEzIUIw/tNviJpNoxOlwKxHoMkInoqmG8eqA7RW0z95lafspThlKY=@vger.kernel.org X-Gm-Message-State: AOJu0Yy/aqArckZhvysB3H0YWsA31RA/8ojki3PUNSkdckhjDV7YYL9s kIH+Mgia4dkBkmRr69jk+igoUTCtA0Q9vH9x1hk1/pKnMXYG91xJw9pc/G10vWN9RjdU2tjRF94 NPA== X-Google-Smtp-Source: AGHT+IFmXbyoB2zLuG6R4z8qhunshoOwoK13liFzIrD6zfHfTgWx575xZoSL1MnlHCxkGXdM9TNGIb7dzpM= X-Received: from oablc15.prod.google.com ([2002:a05:6871:418f:b0:2bc:60dd:3800]) (user=ctshao job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6830:6205:b0:727:3111:1412 with SMTP id 46e09a7af769-7289d17e470mr310076a34.24.1740423027409; Mon, 24 Feb 2025 10:50:27 -0800 (PST) Date: Mon, 24 Feb 2025 10:42:49 -0800 In-Reply-To: <20250224184742.4144931-1-ctshao@google.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250224184742.4144931-1-ctshao@google.com> X-Mailer: git-send-email 2.48.1.658.g4767266eb4-goog Message-ID: <20250224184742.4144931-3-ctshao@google.com> Subject: [PATCH v7 2/4] perf lock: Retrieve owner callstack in bpf program From: Chun-Tse Shao To: linux-kernel@vger.kernel.org Cc: Chun-Tse Shao , peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, nick.forrington@arm.com, linux-perf-users@vger.kernel.org, bpf@vger.kernel.org This implements per-callstack aggregation of lock owners in addition to per-thread. The owner callstack is captured using `bpf_get_task_stack()` at `contention_begin()` and it also adds a custom stackid function for the owner stacks to be compared easily. The owner info is kept in a hash map using lock addr as a key to handle multiple waiters for the same lock. At `contention_end()`, it updates the owner lock stat based on the info that was saved at `contention_begin()`. If there are more waiters, it'd update the owner pid to itself as `contention_end()` means it gets the lock now. But it also needs to check the return value of the lock function in case task was killed by a signal or something. Signed-off-by: Chun-Tse Shao --- .../perf/util/bpf_skel/lock_contention.bpf.c | 212 +++++++++++++++++- 1 file changed, 203 insertions(+), 9 deletions(-) diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 23fe9cc980ae..69be7a4234e0 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -197,6 +197,9 @@ int data_fail; int task_map_full; int data_map_full; +struct task_struct *bpf_task_from_pid(s32 pid) __ksym __weak; +void bpf_task_release(struct task_struct *p) __ksym __weak; + static inline __u64 get_current_cgroup_id(void) { struct task_struct *task; @@ -420,6 +423,61 @@ static inline struct tstamp_data *get_tstamp_elem(__u32 flags) return pelem; } +static inline s32 get_owner_stack_id(u64 *stacktrace) +{ + s32 *id, new_id; + static s64 id_gen = 1; + + id = bpf_map_lookup_elem(&owner_stacks, stacktrace); + if (id) + return *id; + + new_id = (s32)__sync_fetch_and_add(&id_gen, 1); + + bpf_map_update_elem(&owner_stacks, stacktrace, &new_id, BPF_NOEXIST); + + id = bpf_map_lookup_elem(&owner_stacks, stacktrace); + if (id) + return *id; + + return -1; +} + +static inline void update_contention_data(struct contention_data *data, u64 duration, u32 count) +{ + __sync_fetch_and_add(&data->total_time, duration); + __sync_fetch_and_add(&data->count, count); + + /* FIXME: need atomic operations */ + if (data->max_time < duration) + data->max_time = duration; + if (data->min_time > duration) + data->min_time = duration; +} + +static inline void update_owner_stat(u32 id, u64 duration, u32 flags) +{ + struct contention_key key = { + .stack_id = id, + .pid = 0, + .lock_addr_or_cgroup = 0, + }; + struct contention_data *data = bpf_map_lookup_elem(&owner_stat, &key); + + if (!data) { + struct contention_data first = { + .total_time = duration, + .max_time = duration, + .min_time = duration, + .count = 1, + .flags = flags, + }; + bpf_map_update_elem(&owner_stat, &key, &first, BPF_NOEXIST); + } else { + update_contention_data(data, duration, 1); + } +} + SEC("tp_btf/contention_begin") int contention_begin(u64 *ctx) { @@ -437,6 +495,72 @@ int contention_begin(u64 *ctx) pelem->flags = (__u32)ctx[1]; if (needs_callstack) { + u32 i = 0; + u32 id = 0; + int owner_pid; + u64 *buf; + struct task_struct *task; + struct owner_tracing_data *otdata; + + if (!lock_owner) + goto skip_owner; + + task = get_lock_owner(pelem->lock, pelem->flags); + if (!task) + goto skip_owner; + + owner_pid = BPF_CORE_READ(task, pid); + + buf = bpf_map_lookup_elem(&stack_buf, &i); + if (!buf) + goto skip_owner; + for (i = 0; i < max_stack; i++) + buf[i] = 0x0; + + if (!bpf_task_from_pid) + goto skip_owner; + + task = bpf_task_from_pid(owner_pid); + if (!task) + goto skip_owner; + + bpf_get_task_stack(task, buf, max_stack * sizeof(unsigned long), 0); + bpf_task_release(task); + + otdata = bpf_map_lookup_elem(&owner_data, &pelem->lock); + id = get_owner_stack_id(buf); + + /* + * Contention just happens, or corner case `lock` is owned by process not + * `owner_pid`. For the corner case we treat it as unexpected internal error and + * just ignore the precvious tracing record. + */ + if (!otdata || otdata->pid != owner_pid) { + struct owner_tracing_data first = { + .pid = owner_pid, + .timestamp = pelem->timestamp, + .count = 1, + .stack_id = id, + }; + bpf_map_update_elem(&owner_data, &pelem->lock, &first, BPF_ANY); + } + /* Contention is ongoing and new waiter joins */ + else { + __sync_fetch_and_add(&otdata->count, 1); + + /* + * The owner is the same, but stacktrace might be changed. In this case we + * store/update `owner_stat` based on current owner stack id. + */ + if (id != otdata->stack_id) { + update_owner_stat(id, pelem->timestamp - otdata->timestamp, + pelem->flags); + + otdata->timestamp = pelem->timestamp; + otdata->stack_id = id; + } + } +skip_owner: pelem->stack_id = bpf_get_stackid(ctx, &stacks, BPF_F_FAST_STACK_CMP | stack_skip); if (pelem->stack_id < 0) @@ -473,6 +597,7 @@ int contention_end(u64 *ctx) struct tstamp_data *pelem; struct contention_key key = {}; struct contention_data *data; + __u64 timestamp; __u64 duration; bool need_delete = false; @@ -500,12 +625,88 @@ int contention_end(u64 *ctx) need_delete = true; } - duration = bpf_ktime_get_ns() - pelem->timestamp; + timestamp = bpf_ktime_get_ns(); + duration = timestamp - pelem->timestamp; if ((__s64)duration < 0) { __sync_fetch_and_add(&time_fail, 1); goto out; } + if (needs_callstack && lock_owner) { + struct owner_tracing_data *otdata = bpf_map_lookup_elem(&owner_data, &pelem->lock); + + if (!otdata) + goto skip_owner; + + /* Update `owner_stat` */ + update_owner_stat(otdata->stack_id, timestamp - otdata->timestamp, pelem->flags); + + /* No contention is occurring, delete `lock` entry in `owner_data` */ + if (otdata->count <= 1) + bpf_map_delete_elem(&owner_data, &pelem->lock); + /* + * Contention is still ongoing, with a new owner (current task). `owner_data` + * should be updated accordingly. + */ + else { + u32 i = 0; + s32 ret = (s32)ctx[1]; + u64 *buf; + + otdata->timestamp = timestamp; + __sync_fetch_and_add(&otdata->count, -1); + + buf = bpf_map_lookup_elem(&stack_buf, &i); + if (!buf) + goto skip_owner; + for (i = 0; i < (u32)max_stack; i++) + buf[i] = 0x0; + + /* + * `ret` has the return code of the lock function. + * If `ret` is negative, the current task terminates lock waiting without + * acquiring it. Owner is not changed, but we still need to update the owner + * stack. + */ + if (ret < 0) { + s32 id = 0; + struct task_struct *task; + + if (!bpf_task_from_pid) + goto skip_owner; + + task = bpf_task_from_pid(otdata->pid); + if (!task) + goto skip_owner; + + bpf_get_task_stack(task, buf, + max_stack * sizeof(unsigned long), 0); + bpf_task_release(task); + + id = get_owner_stack_id(buf); + + /* + * If owner stack is changed, update owner stack id for this lock. + */ + if (id != otdata->stack_id) + otdata->stack_id = id; + } + /* + * Otherwise, update tracing data with the current task, which is the new + * owner. + */ + else { + otdata->pid = pid; + /* + * We don't want to retrieve callstack here, since it is where the + * current task acquires the lock and provides no additional + * information. We simply assign -1 to invalidate it. + */ + otdata->stack_id = -1; + } + } + } +skip_owner: switch (aggr_mode) { case LOCK_AGGR_CALLER: key.stack_id = pelem->stack_id; @@ -589,14 +790,7 @@ int contention_end(u64 *ctx) } found: - __sync_fetch_and_add(&data->total_time, duration); - __sync_fetch_and_add(&data->count, 1); - - /* FIXME: need atomic operations */ - if (data->max_time < duration) - data->max_time = duration; - if (data->min_time > duration) - data->min_time = duration; + update_contention_data(data, duration, 1); out: pelem->lock = 0;