From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (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 458B046AF03 for ; Tue, 4 Aug 2026 14:03:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785852241; cv=none; b=qJ/if7ByfDBsQjy6OBcJbTjnZ+saohBLZvfC81cTkVRfgEGzkq36s87w4UHDkwjliplwVtCM7iTZjgg09YRZNvwW8lcjtQTq/QwD6pZeAjNj+pWMBCiuBvLTlV1hJssv7RED5h3ZNAOsUtRd+M2ClC2CxPTgc8M31EOh5GuOtoE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785852241; c=relaxed/simple; bh=gAxmUXxonnyTb1ML02g71HD++Ag+MWMb9gtk5XKi+VI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ot7oOziQe02+hceOyjlODY98ZMRblLgNnYOvKMOHf08OSCc3c8qxy1cW6Lm1XxVHM+8sCAm4uQfdpJ2L65hbemKnxstrUGyyLIpV6sWXSTNpBzZpLW7wbp4xyKFFUwq61UX1PYlwRhY2GYvjKEUf2gF7AHXsil/3OeGbkLPGhDs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=k6EVTpwF; arc=none smtp.client-ip=209.85.128.70 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--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="k6EVTpwF" Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4955ce558d8so33962165e9.3 for ; Tue, 04 Aug 2026 07:03:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785852237; x=1786457037; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=UowPlZ8bZ1cpN+rdzysaXkXW4M7Wma5JPRhoyN5DsfY=; b=k6EVTpwFEveW8BCU08pDX4Ocd86byh1PiXQoHS8oNczX52JoK/P+5/o7DswQkVhets Sob3v1B59ET7B9wbp4p/kmkfp6lvLfrCAyvJJkiy8uLPrW+yR8rLx9Kndrig3i3hFhd+ JGqj9qTw/aD4gahV4YXmSgXkzcG92vs2afppfBCBesaq0TPGor54PdsOCkiY+Uwk99i2 lDeDnbzL6gRCRgJOHHiUDsljHWvvpSsxWse44P9e4sikUEMbly5zWCUDdXbAiSbbIyJY dUeb4vR0O1oMtUxf/xSArXRog/0+ViCDh8M8LHNbXTBYfvIw2MCbkW7RlvEJOPjNg4No M2Lg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785852237; x=1786457037; h=content-type: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:content-type; bh=UowPlZ8bZ1cpN+rdzysaXkXW4M7Wma5JPRhoyN5DsfY=; b=MHCcqpJEHeTdYo7xEqmNCG+xOyyVgPyNTba3iwukqOBJtXBOO/t6SQ+L4U/4rqaKvD FbG4/AgCLqDUmUALQzaP0u1IiN071QMX3Zo0UHQ8/lYYN63QthJzlTKjzH0tErnT+5aA WYyb1RpQbRuRFfYBUQuFKRmYtk6LSUUNp2F6RjRJlUvvf5Wh9qVTdGycUpmolj5FyejD Y22LmExEKIpDRCHdZTVV0o0s9BA4yeDDvEkoN+sPv7HO1A/Qyj72+foaIIzzcth3012/ stTeYUvBIlesdynsC9U7VFZs8+qW2ZMiOBH891euta8dJz3tUL6kqVSonwg1xfD+XlEv L2rQ== X-Forwarded-Encrypted: i=1; AHgh+RrDRlaJzBwit3KzGgzpZSCUMlaNlXMNQjyquUHvmFFr+QKV7F/0ZOScpESoXh9mRDWgpgOYANn+oRpNHlY=@vger.kernel.org X-Gm-Message-State: AOJu0YyeR9EEvqm//MNvNkVi36kXEGekeRjphU9zZEShs/ebEFIlkIGZ GUF0pnazt0G4i9Pm8lcQu7C4i+uhJ9mB5Qt83fb5JOx2b83LPv0u2rAfWb3eKy2mB+b/bHCx/ue BOD2ojODtp8KkykzVmEl6RQ== X-Received: from wmqd6.prod.google.com ([2002:a05:600c:34c6:b0:495:4aa0:4b5]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4445:b0:493:a438:7f98 with SMTP id 5b1f17b1804b1-4980c694df5mr289599095e9.18.1785852237299; Tue, 04 Aug 2026 07:03:57 -0700 (PDT) Date: Tue, 4 Aug 2026 15:03:20 +0100 In-Reply-To: <20260804140333.797210-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260804140333.797210-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.571.g244d577d93-goog Message-ID: <20260804140333.797210-6-vdonnefort@google.com> Subject: [PATCH v4 05/18] tracing/simple_ring_buffer: Add support for compressed length From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" The array length is the total size in bytes of the data for the current event. It is possible to compress this value into the event header type, which has 28 unused types, saving 32 bits for sufficiently small events. The compressed length is expressed as a multiple of the ring-buffer alignment, 4-bytes by default. Enforce this alignment. Signed-off-by: Vincent Donnefort diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index f4642f5adda3..1a97d17cca24 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -207,7 +207,15 @@ static unsigned long rb_event_size(unsigned long length) { struct ring_buffer_event *event; - return length + RB_EVNT_HDR_SIZE + sizeof(event->array[0]); + if (!length) + length++; + + length = ALIGN(length, RB_ALIGNMENT); + + if (length > RB_MAX_SMALL_DATA) + length += sizeof(event->array[0]); + + return length + RB_EVNT_HDR_SIZE; } static struct ring_buffer_event * @@ -223,12 +231,15 @@ rb_event_add_ts_extend(struct ring_buffer_event *event, u64 delta) static struct ring_buffer_event * simple_rb_reserve_next(struct simple_rb_per_cpu *cpu_buffer, unsigned long length, u64 timestamp) { - unsigned long ts_ext_size = 0, event_size = rb_event_size(length); struct simple_buffer_page *tail = cpu_buffer->tail_page; + unsigned long event_size, array_size, ts_ext_size = 0; struct ring_buffer_event *event; u32 write, prev_write; u64 time_delta; + event_size = rb_event_size(length); + array_size = event_size - RB_EVNT_HDR_SIZE; + time_delta = timestamp - cpu_buffer->write_stamp; if (test_time_stamp(time_delta)) @@ -259,9 +270,13 @@ simple_rb_reserve_next(struct simple_rb_per_cpu *cpu_buffer, unsigned long lengt time_delta = 0; } - event->type_len = 0; + if (length > RB_MAX_SMALL_DATA) { + event->type_len = 0; + event->array[0] = array_size; + } else { + event->type_len = DIV_ROUND_UP(array_size, RB_ALIGNMENT); + } event->time_delta = time_delta; - event->array[0] = event_size - RB_EVNT_HDR_SIZE; return event; } @@ -284,7 +299,7 @@ void *simple_ring_buffer_reserve(struct simple_rb_per_cpu *cpu_buffer, unsigned rb_event = simple_rb_reserve_next(cpu_buffer, length, timestamp); - return &rb_event->array[1]; + return rb_event->type_len ? &rb_event->array[0] : &rb_event->array[1]; } EXPORT_SYMBOL_GPL(simple_ring_buffer_reserve); -- 2.55.0.571.g244d577d93-goog