From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) (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 A81C92907; Thu, 9 May 2024 19:55:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715284544; cv=none; b=kQ2I9OhrvYH8we45ISEIRko5o6uvBnNwYRNsLmtjHPPPmNrGo9ZM9hYwfdyKPFVWXco3dYcmQYwm0gYGlwDgDvlcY9P1AgOYEEsISSzLIzv/Yt5FBLNrvNzlbPbrgsqmr4648HkQSIrZtOyb8QQN1LU7kF5M1Z1tZify+rnbzjE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715284544; c=relaxed/simple; bh=zbu/IGQfUBc/Eq+bOd62MWZ17jU/HCjaq7V/oU5X5d8=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=os4QJe/0xyk//XFXcWjQ97nMoe36UL0S3nJF60B+/YVl9Q9RhNSKqocu+hKv5c2Ca2IM6SERLB6X2hfi7b29Epz9xlCl8Q69C3hF0iWH8YEJrI4ftBKlNPo+wpkamaqZ/3HcKXxM/dYmwuLUyCxCCHL3obd7aGcBZ7CKT7M85rc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.216.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pj1-f47.google.com with SMTP id 98e67ed59e1d1-2b37731c118so1070809a91.1; Thu, 09 May 2024 12:55:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715284542; x=1715889342; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=O/Ml7CX2KT81liQorKyRALPGhqTOeMdtMPyFG6ydCgw=; b=VSd0+KZzC/deghSAqirUr7t/13riAszeZPxmdRxBzJ4qOn4X4iLTTsDFI0rlosHxOy jr3gBOUn2cbznQYaUOB+8TyyQhdBOLuX92NCCm7F7IE2V0xQ0rIhlR9e4LakRqmd8nb2 e0oVlHJMzM2+b8sNSf0buczGqqirFhmJ/ww5YojRjRyrenPUKZ5IQORQgqhsTiHAJlJ6 dtUiWV61UO9BFg6Jm8WzJuVyCZDNTr/UT9T7h5RsQENzp+Z8n7E3PZ6RI5THqDuyej9Z IKrezniSZN5yois9ppgWL7ICXVdqMpaVey9VTV11CjNxmml4t9nyxIeUwcINT3ITVqlp BvgA== X-Forwarded-Encrypted: i=1; AJvYcCV+pIsTjnYTRyiHCYTe/hzB4KIULt9oWId9MGyBX4VfvnQ95I7/HUv0gO/Omi7GD0SAYLTrr8mDs67am+bYSmAx6Ejb1qizKWcHb2oQPZ8lVVWCJnkRQMDKhYb1GwtJDyOTitEDnJJv6b2p2MtYewJq89/anQmMzN5v0cn8+gDjYGoJdQ== X-Gm-Message-State: AOJu0YyfH3j2pWgnkkINXl+b11WvBUfiUYNxnSIauJgNIjxK3W3iAwR9 91x1wHbAJ1L1ofUSElGhZci2OfKel9jAFnxIcgGWJDlDBRerV9U8vTDRa3X/V1RP11wolekScK5 zxXgPGWoXMhPX6/QWIgb70ul4tnk= X-Google-Smtp-Source: AGHT+IGQnK5k9VmctCtJUB7NtGIF2piUgInCtKQzIzp36Q/QXeaOWXRPQeFgx7BkHN2t9nR29dSOVZBvNnQzxcoaRrE= X-Received: by 2002:a17:90a:17c4:b0:2a9:f861:223e with SMTP id 98e67ed59e1d1-2b6cc7800edmr460740a91.29.1715284541779; Thu, 09 May 2024 12:55:41 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240502000602.753861-1-yabinc@google.com> In-Reply-To: From: Namhyung Kim Date: Thu, 9 May 2024 12:55:30 -0700 Message-ID: Subject: Re: [PATCH v2] perf/core: Save raw sample data conditionally based on sample type To: Yabin Cui Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Another thought. On Thu, May 9, 2024 at 12:45=E2=80=AFPM Namhyung Kim = wrote: > > Hello, > > On Wed, May 1, 2024 at 5:06=E2=80=AFPM Yabin Cui wrot= e: > > > > Currently, space for raw sample data is always allocated within sample > > records for both BPF output and tracepoint events. This leads to unused > > space in sample records when raw sample data is not requested. > > Oh, I thought it was ok because even if it sets _RAW bit in the > data->sample_flags unconditionally, perf_prepare_sample() and > perf_output_sample() checks the original event's attr->sample_type > so the raw data won't be recorded. > > But I've realized that it increased data->dyn_size already. :( > Which means the sample would have garbage at the end. > > I need to check if there are other places that made the same > mistake for other sample types. > > > > > This patch checks sample type of an event before saving raw sample data > > in both BPF output and tracepoint event handling logic. Raw sample data > > will only be saved if explicitly requested, reducing overhead when it > > is not needed. > > > > Fixes: 0a9081cf0a11 ("perf/core: Add perf_sample_save_raw_data() helper= ") > > Signed-off-by: Yabin Cui > > Acked-by: Namhyung Kim > > Thanks, > Namhyung > > > --- [SNIP] > > @@ -10180,13 +10181,18 @@ static void __perf_tp_event_target_task(u64 c= ount, void *record, > > /* Cannot deliver synchronous signal to other task. */ > > if (event->attr.sigtrap) > > return; > > - if (perf_tp_event_match(event, data, regs)) > > + if (perf_tp_event_match(event, raw, regs)) { > > + perf_sample_data_init(data, 0, 0); > > + if (event->attr.sample_type & PERF_SAMPLE_RAW) > > + perf_sample_save_raw_data(data, raw); Hmm.. to prevent future mistakes, maybe we can move the check into the perf_sample_save_raw_data() itself. And it'd be great if you could do the same for callchain and brstack too. :) Thanks, Namhyung > > perf_swevent_event(event, count, data, regs); > > + } > > } > > > > static void perf_tp_event_target_task(u64 count, void *record, > > struct pt_regs *regs, > > struct perf_sample_data *data, > > + struct perf_raw_record *raw, > > struct perf_event_context *ctx) > > { > > unsigned int cpu =3D smp_processor_id(); > > @@ -10194,15 +10200,15 @@ static void perf_tp_event_target_task(u64 cou= nt, void *record, > > struct perf_event *event, *sibling; > > > > perf_event_groups_for_cpu_pmu(event, &ctx->pinned_groups, cpu, = pmu) { > > - __perf_tp_event_target_task(count, record, regs, data, = event); > > + __perf_tp_event_target_task(count, record, regs, data, = raw, event); > > for_each_sibling_event(sibling, event) > > - __perf_tp_event_target_task(count, record, regs= , data, sibling); > > + __perf_tp_event_target_task(count, record, regs= , data, raw, sibling); > > } > > > > perf_event_groups_for_cpu_pmu(event, &ctx->flexible_groups, cpu= , pmu) { > > - __perf_tp_event_target_task(count, record, regs, data, = event); > > + __perf_tp_event_target_task(count, record, regs, data, = raw, event); > > for_each_sibling_event(sibling, event) > > - __perf_tp_event_target_task(count, record, regs= , data, sibling); > > + __perf_tp_event_target_task(count, record, regs= , data, raw, sibling); > > } > > } > > > > @@ -10220,15 +10226,10 @@ void perf_tp_event(u16 event_type, u64 count,= void *record, int entry_size, > > }, > > }; > > > > - perf_sample_data_init(&data, 0, 0); > > - perf_sample_save_raw_data(&data, &raw); > > - > > perf_trace_buf_update(record, event_type); > > > > hlist_for_each_entry_rcu(event, head, hlist_entry) { > > - if (perf_tp_event_match(event, &data, regs)) { > > - perf_swevent_event(event, count, &data, regs); > > - > > + if (perf_tp_event_match(event, &raw, regs)) { > > /* > > * Here use the same on-stack perf_sample_data, > > * some members in data are event-specific and > > @@ -10238,7 +10239,9 @@ void perf_tp_event(u16 event_type, u64 count, v= oid *record, int entry_size, > > * because data->sample_flags is set. > > */ > > perf_sample_data_init(&data, 0, 0); > > - perf_sample_save_raw_data(&data, &raw); > > + if (event->attr.sample_type & PERF_SAMPLE_RAW) > > + perf_sample_save_raw_data(&data, &raw); > > + perf_swevent_event(event, count, &data, regs); > > } > > } > > > > @@ -10255,7 +10258,7 @@ void perf_tp_event(u16 event_type, u64 count, v= oid *record, int entry_size, > > goto unlock; > > > > raw_spin_lock(&ctx->lock); > > - perf_tp_event_target_task(count, record, regs, &data, c= tx); > > + perf_tp_event_target_task(count, record, regs, &data, &= raw, ctx); > > raw_spin_unlock(&ctx->lock); > > unlock: > > rcu_read_unlock(); > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > index 9dc605f08a23..4b3ff71b4c0a 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -620,7 +620,8 @@ static const struct bpf_func_proto bpf_perf_event_r= ead_value_proto =3D { > > > > static __always_inline u64 > > __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map, > > - u64 flags, struct perf_sample_data *sd) > > + u64 flags, struct perf_raw_record *raw, > > + struct perf_sample_data *sd) > > { > > struct bpf_array *array =3D container_of(map, struct bpf_array,= map); > > unsigned int cpu =3D smp_processor_id(); > > @@ -645,6 +646,9 @@ __bpf_perf_event_output(struct pt_regs *regs, struc= t bpf_map *map, > > if (unlikely(event->oncpu !=3D cpu)) > > return -EOPNOTSUPP; > > > > + if (event->attr.sample_type & PERF_SAMPLE_RAW) > > + perf_sample_save_raw_data(sd, raw); > > + > > return perf_event_output(event, sd, regs); > > } > > > > @@ -688,9 +692,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *,= regs, struct bpf_map *, map, > > } > > > > perf_sample_data_init(sd, 0, 0); > > - perf_sample_save_raw_data(sd, &raw); > > > > - err =3D __bpf_perf_event_output(regs, map, flags, sd); > > + err =3D __bpf_perf_event_output(regs, map, flags, &raw, sd); > > out: > > this_cpu_dec(bpf_trace_nest_level); > > preempt_enable(); > > @@ -749,9 +752,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags= , void *meta, u64 meta_size, > > > > perf_fetch_caller_regs(regs); > > perf_sample_data_init(sd, 0, 0); > > - perf_sample_save_raw_data(sd, &raw); > > > > - ret =3D __bpf_perf_event_output(regs, map, flags, sd); > > + ret =3D __bpf_perf_event_output(regs, map, flags, &raw, sd); > > out: > > this_cpu_dec(bpf_event_output_nest_level); > > preempt_enable(); > > -- > > 2.45.0.rc0.197.gbae5840b3b-goog > >