From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 843D722FE0E; Tue, 14 Jan 2025 03:05:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736823936; cv=none; b=q1lxtmlKwWiuZWDxySgwOPo8nYZo4yOO8MJn3Gr2F9vi4sI0WWus7TRS6Bn3HkWjoFLd+Ul9l/ynQkRi18H5crrc3Lq7tvyRpdIS+/Hhz5ZdfPlNEdlixRpIv/rUmTIn3XcuCpC2ARLkZ00Jp1MCT4Dn6sgnAuxHkvQUfqq+/k0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736823936; c=relaxed/simple; bh=D8Z5h+E1QWlcD9w8w1Q9u7XfIh6Yamede78jjfxklPA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h9lYRrxGYUugkeZYZ0vW3cmjQBOxy6XIPy+25YXvp6nVTE+baJQL8dcxCFzkQUHKlL+X5qGy/ZMqOc1jVQW90i4BLLO/CHL+FDz6pK2qbVnHjffSMjVOCMePX3QDbXlI2RaIXOpjeLO3hecMzyRRRRwlkfDmy59TKAJEq8LvUJM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YEMBjex5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YEMBjex5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D01EC4CED6; Tue, 14 Jan 2025 03:05:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736823936; bh=D8Z5h+E1QWlcD9w8w1Q9u7XfIh6Yamede78jjfxklPA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YEMBjex5KVXN/i4hXvp5gJyRkZGKFKilElxR+jpcYJXi71061VcFjlbBfyafT0bUl 7idzRNUnxIk6YDLOaAtx1tZTqIbwqlvoBFfPJBmseaTcqDC1s5u46KHUqaDam3UffR rKwtq0R3DBqYIk3gJjutCA+eygEkJ6eO8xDUOjLb7yLSadTY+1gd1Ns5ZqMctc+8sB FsEcLjgI74YgspTcjw7DxTOnaPxOioD9lU3WifCqovVOpnsDcfF8UuuQ+xfx/BQK55 Erlt9qtol0E8RSnb3iljlfhpRWTcUENe/9ceDYlNjSDooZBBPnsXzPtaDo+CWsRrk8 qsASCELxuHP4g== Date: Mon, 13 Jan 2025 19:05:34 -0800 From: Namhyung Kim To: Chun-Tse Shao Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com, acme@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, linux-perf-users@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH v2 1/4] perf lock: Add bpf maps for owner stack tracing Message-ID: References: <20250113052220.2105645-1-ctshao@google.com> <20250113052220.2105645-2-ctshao@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250113052220.2105645-2-ctshao@google.com> Hello, On Sun, Jan 12, 2025 at 09:20:14PM -0800, Chun-Tse Shao wrote: > Add few bpf maps in order to tracing owner stack. If you want to split this code as a separate commit, I think you'd better explain what these maps do and why you need them. > > Signed-off-by: Chun-Tse Shao > --- > tools/perf/util/bpf_lock_contention.c | 17 ++++++-- > .../perf/util/bpf_skel/lock_contention.bpf.c | 40 +++++++++++++++++-- > tools/perf/util/bpf_skel/lock_data.h | 6 +++ > 3 files changed, 56 insertions(+), 7 deletions(-) > > diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c > index 41a1ad087895..c9c58f243ceb 100644 > --- a/tools/perf/util/bpf_lock_contention.c > +++ b/tools/perf/util/bpf_lock_contention.c > @@ -41,9 +41,20 @@ int lock_contention_prepare(struct lock_contention *con) > else > bpf_map__set_max_entries(skel->maps.task_data, 1); > > - if (con->save_callstack) > - bpf_map__set_max_entries(skel->maps.stacks, con->map_nr_entries); > - else > + if (con->save_callstack) { > + bpf_map__set_max_entries(skel->maps.stacks, > + con->map_nr_entries); > + if (con->owner) { > + bpf_map__set_value_size(skel->maps.owner_stacks_entries, > + con->max_stack * sizeof(u64)); > + bpf_map__set_value_size( > + skel->maps.contention_owner_stacks, > + con->max_stack * sizeof(u64)); > + bpf_map__set_key_size(skel->maps.owner_lock_stat, > + con->max_stack * sizeof(u64)); > + skel->rodata->max_stack = con->max_stack; > + } > + } else > bpf_map__set_max_entries(skel->maps.stacks, 1); > > if (target__has_cpu(target)) { > diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c > index 1069bda5d733..05da19fdab23 100644 > --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c > +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c > @@ -19,13 +19,37 @@ > #define LCB_F_PERCPU (1U << 4) > #define LCB_F_MUTEX (1U << 5) > Can we rename these shorter and save some typings? > -/* callstack storage */ > + /* tmp buffer for owner callstack */ > struct { > - __uint(type, BPF_MAP_TYPE_STACK_TRACE); > + __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY); > __uint(key_size, sizeof(__u32)); > __uint(value_size, sizeof(__u64)); > + __uint(max_entries, 1); > +} owner_stacks_entries SEC(".maps"); I think this can be 'stack_buf'. > + > +/* a map for tracing lock address to owner data */ > +struct { > + __uint(type, BPF_MAP_TYPE_HASH); > + __uint(key_size, sizeof(__u64)); // lock address > + __uint(value_size, sizeof(cotd)); > __uint(max_entries, MAX_ENTRIES); > -} stacks SEC(".maps"); > +} contention_owner_tracing SEC(".maps"); owner_data. > + > +/* a map for tracing lock address to owner stacktrace */ > +struct { > + __uint(type, BPF_MAP_TYPE_HASH); > + __uint(key_size, sizeof(__u64)); // lock address > + __uint(value_size, sizeof(__u64)); // straktrace Typo. > + __uint(max_entries, MAX_ENTRIES); > +} contention_owner_stacks SEC(".maps"); owner_stack. > + > +/* owner callstack to contention data storage */ > +struct { > + __uint(type, BPF_MAP_TYPE_HASH); > + __uint(key_size, sizeof(__u64)); > + __uint(value_size, sizeof(struct contention_data)); > + __uint(max_entries, MAX_ENTRIES); > +} owner_lock_stat SEC(".maps"); owner_stat. What do you think? By the way, I got an idea to implement stackid map in BPF using hash map. For owner stack, you can use the stacktrace as a key and make a value an unique integer. Then the return value can be used as a stack id (like from bpf_get_stackid) for the owner_data and owner_stat. Something like: s32 get_stack_id(struct owner_stack *owner_stack, u64 stacktrace[]) { s32 *id, new_id; static s32 id_gen = 1; id = bpf_map_lookup_elem(owner_stack, stacktrace); if (id) return *id; new_id = __sync_fetch_and_add(&id_gen, 1); bpf_map_update_elem(owner_stack, stacktrace, &new_id, BPF_NOEXIST); id = bpf_map_lookup_elem(owner_stack, stacktrace); if (id) return *id; return -1; } Later, in user space, you can traverse the owner_stack map to build reverse mapping from id to stacktrace. > > /* maintain timestamp at the beginning of contention */ > struct { > @@ -43,6 +67,14 @@ struct { > __uint(max_entries, 1); > } tstamp_cpu SEC(".maps"); > > +/* callstack storage */ > +struct { > + __uint(type, BPF_MAP_TYPE_STACK_TRACE); > + __uint(key_size, sizeof(__u32)); > + __uint(value_size, sizeof(__u64)); > + __uint(max_entries, MAX_ENTRIES); > +} stacks SEC(".maps"); > + > /* actual lock contention statistics */ > struct { > __uint(type, BPF_MAP_TYPE_HASH); > @@ -126,6 +158,7 @@ const volatile int needs_callstack; > const volatile int stack_skip; > const volatile int lock_owner; > const volatile int use_cgroup_v2; > +const volatile int max_stack; > > /* determine the key of lock stat */ > const volatile int aggr_mode; > @@ -436,7 +469,6 @@ int contention_end(u64 *ctx) > return 0; > need_delete = true; > } > - > duration = bpf_ktime_get_ns() - pelem->timestamp; > if ((__s64)duration < 0) { > __sync_fetch_and_add(&time_fail, 1); > diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h > index de12892f992f..1ef0bca9860e 100644 > --- a/tools/perf/util/bpf_skel/lock_data.h > +++ b/tools/perf/util/bpf_skel/lock_data.h > @@ -3,6 +3,12 @@ > #ifndef UTIL_BPF_SKEL_LOCK_DATA_H > #define UTIL_BPF_SKEL_LOCK_DATA_H > > +typedef struct contention_owner_tracing_data { > + u32 pid; // Who has the lock. > + u64 timestamp; // The time while the owner acquires lock and contention is going on. > + u32 count; // How many waiters for this lock. Switching the order of timestamp and count would remove padding. > +} cotd; Usually we don't use typedef to remove the struct tag. Thanks, Namhyung > + > struct tstamp_data { > u64 timestamp; > u64 lock; > -- > 2.47.1.688.g23fc6f90ad-goog >