From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 35744CAC597 for ; Mon, 15 Sep 2025 14:30:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uyADA-00069P-N5; Mon, 15 Sep 2025 10:29:44 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uyAD1-00062I-DM for qemu-devel@nongnu.org; Mon, 15 Sep 2025 10:29:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uyACj-0000hU-RT for qemu-devel@nongnu.org; Mon, 15 Sep 2025 10:29:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757946553; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fkNO4jGwChegh76twsuNkCoBzxs6Ya8SUNtkNdLv+LU=; b=e0R+bKpvauHk573LjzcW4ioDAO8Cd+5EUBswpJ37mbucsATYlRBM/8vVWUgB9v+ihr6sUv akNNYGpXtzciEpW0CuT8GCGqeF1uEkfLs9ntgQR6sQvcinR5F6huIajgF9SbdtNh1uSBtk Utn25QDTul4pVIEu5XF+nxIznJRZUVk= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-83-Da2rmTPQOKmm0aU5orzMaw-1; Mon, 15 Sep 2025 10:29:09 -0400 X-MC-Unique: Da2rmTPQOKmm0aU5orzMaw-1 X-Mimecast-MFC-AGG-ID: Da2rmTPQOKmm0aU5orzMaw_1757946547 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4FEED180028D; Mon, 15 Sep 2025 14:29:07 +0000 (UTC) Received: from localhost (unknown [10.2.16.109]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7620E18004A3; Mon, 15 Sep 2025 14:29:06 +0000 (UTC) Date: Mon, 15 Sep 2025 10:29:05 -0400 From: Stefan Hajnoczi To: Markus Armbruster Cc: qemu-devel@nongnu.org, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Mads Ynddal , Paolo Bonzini , Alex =?iso-8859-1?Q?Benn=E9e?= , Peter Maydell , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Greg Kurz Subject: Re: The different ways QEMU logs stuff Message-ID: <20250915142905.GB69944@fedora> References: <87bjnhgpg8.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="4u/h+++1dQIE6sWX" Content-Disposition: inline In-Reply-To: <87bjnhgpg8.fsf@pond.sub.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.035, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --4u/h+++1dQIE6sWX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Sep 11, 2025 at 02:10:15PM +0200, Markus Armbruster wrote: > * Tracing vs. "log items" >=20 > Tracing and "log items" both provide opt-in logging. >=20 > Why do we have two? Feels like an accident to me. >=20 > When to use which? I guess people pick whatever they're familiar > with. >=20 > Would we be better off with just one? I wish... >=20 > Which one? Clearly tracing, because tracing backends provide plenty > of useful functionality "log items" lack. >=20 > "Log items" support per-thread log files. With tracing, you could > instead split by thread names once Daniel's series is in. >=20 > Address range filtering is only used with "log items". It could just > as easily be used with tracing. Paolo mentioned that tracing is structured (each event has typed parameters) whereas logging consists of an arbitrary string. The reason for this is that tracers are usually designed for low overhead and for processing trace events. Tracing is used to instrument QEMU for detailed analysis of control flow or performance investigation. It's a different use case from logging although there is some overlap. People like to use tools like perf(1), SystemTap, etc and tracing allows QEMU to support them. It's not a use case where regular log files are used. Stefan --4u/h+++1dQIE6sWX Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmjIIrEACgkQnKSrs4Gr c8ijXwf+PHExVp5pTmOkH88XHdih7+knMgbU8njFecxaWwGGVDBy9DdyeuLV1sdC obuuVZmLTwcaQFuq7QLGVgz9n699xX5ltvZwvvdPCBxoaoSEv/Mtqsfb+IZLlq4s FeKIcGGPsS8nb4Z018UiAS0Repl1qCRCsyXNqkKjRff38F/hfuQvg09dsJam1U/S 2a557g6igAXCX4uOIOs+KfX42G3Bb4X4dGmB9L8jfoSwXYtwq/PC1XfyO4t3MAWR wS6q3p0SAzjq44MKRwW+ZKsbTlSPzvB6P4NPBpfI78wgZupRM2U2sOipwcSLyfdG 4EL7ys1dbopDvFPfe78Ubzzqe8p6cg== =7mv9 -----END PGP SIGNATURE----- --4u/h+++1dQIE6sWX--