From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 84E9F15B130 for ; Wed, 24 Apr 2024 13:12:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713964363; cv=none; b=Oj9VzWW1TzwfWf/NIaPhKOiUKIPrW4Kr12NhqyLZaIL4T5OnqxKRkLJQygwAYV1+aTrICHcfEo0XZD9Jrbhj/ltaIXlCuA7ZiXqE7q22BkHvq2cwXnUmH9LCC/B/uOHl6+Q92RB66/uM7Rl0yf5jg524dDLsB/23IgIb2G/Z7sg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713964363; c=relaxed/simple; bh=Bq7YpiW5Q91ygbccQR6dBgrOfa3wjJXstae79u/flmI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=NG+9FYaiJ6iROWysUkRpdqfXkZchUUcgFgey6EE+XPpiogkfYS4Gum5xwonrYsDn5aW9FQO0wuc02WNT0wXRDXs0+XyNcoyLJuXdlEBZnoJAqjEgjmI5Y/dBnaK+FcPZMRGqQvSBPH5XuWDRhfSz5IGT6Y2axAuWMAF5E8utT3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=f4I+9I2+; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="f4I+9I2+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1713964360; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mnUi2cVgHWx3MxzJaTxsxopOnKpBzB2N1qs3enmhQg8=; b=f4I+9I2+cjA+ktJ51SxWZXNz/gpLgV4lvOnbOSh/FqYSmrR7Jpj9TZ6cglDudFYvT7+2iv 48QoYyIwN3u49QYZQGAN1iD/vFM/jmhHfJmkUTz/Y54uBuUZr18k+6O83jBBiUg17GvwbQ 93BazkdPCdOYiWwFDfFSIS7EpAzmrpY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-355-_flngu1WPLanKjmZSWkVnA-1; Wed, 24 Apr 2024 09:12:36 -0400 X-MC-Unique: _flngu1WPLanKjmZSWkVnA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8CDA118065AA; Wed, 24 Apr 2024 13:12:35 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 69EB840C122D; Wed, 24 Apr 2024 13:12:35 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 5E46921E66C8; Wed, 24 Apr 2024 15:12:34 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: fan , Jonathan Cameron , qemu-devel@nongnu.org, linux-cxl@vger.kernel.org, gregory.price@memverge.com, ira.weiny@intel.com, dan.j.williams@intel.com, a.manzanares@samsung.com, dave@stgolabs.net, nmtadam.samsung@gmail.com, jim.harris@samsung.com, Jorgen.Hansen@wdc.com, wj28.lee@gmail.com, Fan Ni Subject: Re: [PATCH v5 13/13] qapi/cxl.json: Add QMP interfaces to print out accepted and pending DC extents In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Tue, 5 Mar 2024 17:14:57 +0000") References: <20240304194331.1586191-1-nifan.cxl@gmail.com> <20240304194331.1586191-14-nifan.cxl@gmail.com> <20240305160908.000010c5@Huawei.com> Date: Wed, 24 Apr 2024 15:12:34 +0200 Message-ID: <8734ravr99.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Daniel P. Berrang=C3=A9 writes: > On Tue, Mar 05, 2024 at 09:09:05AM -0800, fan wrote: >> On Tue, Mar 05, 2024 at 04:15:30PM +0000, Daniel P. Berrang=C3=A9 wrote: >> > On Tue, Mar 05, 2024 at 04:09:08PM +0000, Jonathan Cameron via wrote: >> > > On Mon, 4 Mar 2024 11:34:08 -0800 >> > > nifan.cxl@gmail.com wrote: >> > >=20 >> > > > From: Fan Ni >> > > >=20 >> > > > With the change, we add the following two QMP interfaces to print = out >> > > > extents information in the device, >> > > > 1. cxl-display-accepted-dc-extents: print out the accepted DC exte= nts in >> > > > the device; >> > > > 2. cxl-display-pending-to-add-dc-extents: print out the pending-to= -add >> > > > DC extents in the device; >> > > > The output is appended to a file passed to the command and by defa= ult >> > > > it is /tmp/dc-extent.txt. >> > > Hi Fan, >> > >=20 >> > > Is there precedence for this sort of logging to a file from a qmp >> > > command? I can see something like this being useful. >> >=20 >> > This is pretty unusual. >>=20 >> Yeah. I cannot find anything similar in existing code, my initial plan >> was to print out to the screen directly, however, cannot find out how to >> do it nicely, so decided to go with a file.=20 >>=20 >> Is there a reason why we do not want to go with this approach? >>=20 >> >=20 >> > For runtime debugging information our strong preference is to integrate >> > 'trace' probes throughout the code: >> >=20 >> > https://www.qemu.org/docs/master/devel/tracing.html#tracing >>=20 >> I am not familiar with the trace mechanism. However, I think the >> approach in this patch may be useful not only for debugging purpose. >> Although not tried yet, maybe we can also use the approach to set >> some parameters at runtime like what procfs does? > > Please don't invent something new unless you can show why QEMU's existing > tracing system isn't sufficiently good for the problem. QEMU's tracing > can dump to the terminal directly, or integrate with a variety of other > backends, and data can be turned off/on at runtime per-trace point. Seconded.