From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B082606A31A for ; Fri, 23 Oct 2026 06:15:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=TqASayei Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xK8YB-0002Mc-Sv; Fri, 23 Oct 2026 02:14:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xK8Xx-0002Dq-IE for qemu-devel@nongnu.org; Fri, 23 Oct 2026 02:14:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xK8Xv-00029w-PI for qemu-devel@nongnu.org; Fri, 23 Oct 2026 02:14:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1792736069; 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=BQlRRoL+Mbl4J2xGHUHD2JQ2GkRxfneVSIZiYITnJOU=; b=TqASayeiENHg9ioFeHMQxY5RoRZ+vFG544pCYKee9BE/R1zwWh3qUN6o20d5eHWUZEHNug a1T7fwGSiJClqujQRPvoYpKQ6oNGv1WMxbEXUxBQIJaU+/KAMhmeSUCZ9TyCvKJbcnIAGn TIv8kXQyE23SuNmBIv54O/6YGj2JJSk= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-460-65ZM1WumOj2q_BvhsLn66A-1; Fri, 23 Oct 2026 02:14:28 -0400 X-MC-Unique: 65ZM1WumOj2q_BvhsLn66A-1 X-Mimecast-MFC-AGG-ID: 65ZM1WumOj2q_BvhsLn66A_1792736067 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7DA601955F44; Fri, 23 Oct 2026 06:14:26 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.5]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D010A180029C; Fri, 23 Oct 2026 06:14:25 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 725F821E6A04; Fri, 23 Oct 2026 08:14:23 +0200 (CEST) From: Markus Armbruster To: Hanna Czenczek Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Kevin Wolf , John Snow , "Denis V . Lunev" , Eric Blake , Stefan Hajnoczi , Paolo Bonzini Subject: Re: [PATCH v2 06/12] qapi/block: Add BLOCK_IO_DELAY event In-Reply-To: <65193d93-2fcc-4a39-8e54-d16022855bbf@redhat.com> (Hanna Czenczek's message of "Thu, 22 Oct 2026 17:55:47 +0200") References: <20261019182028.45305-1-hreitz@redhat.com> <20261019182028.45305-7-hreitz@redhat.com> <87a4o8sw79.fsf@pond.sub.org> <65193d93-2fcc-4a39-8e54-d16022855bbf@redhat.com> Date: Fri, 23 Oct 2026 08:14:23 +0200 Message-ID: <87pkx1gczk.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 2 X-Spam_score: 0.2 X-Spam_bar: / X-Spam_report: (0.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.339, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hanna Czenczek writes: > On 20.10.26 08:49, Markus Armbruster wrote: >> Hanna Czenczek writes: >> >>> This event will be emitted when a disk operation takes longer than a >>> pre-defined threshold (as set on the block device). >>> >>> Note that the description refers to the "delay-report-ns" and >>> "delay-stop-ns" block device properties, which are not yet available. >>> A future commit in this series will add them. >>> >>> Signed-off-by: Hanna Czenczek >>> --- >>> qapi/block.json | 37 +++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 37 insertions(+) >>> >>> diff --git a/qapi/block.json b/qapi/block.json >>> index 8f4a71733c1..5f9f5c28050 100644 >>> --- a/qapi/block.json >>> +++ b/qapi/block.json >>> @@ -649,3 +649,40 @@ >>> ## >>> { 'enum': 'IoAccountingOperation', >>> 'data': [ 'read', 'write', 'flush', 'zone-append', 'unmap' ] } >>> + >>> +## >>> +# @BLOCK_IO_DELAY: >>> +# >>> +# Emitted when a disk operation takes longer than the pre-defined >>> +# threshold (as set via the "delay-report-ns" / "delay-stop-ns" >>> +# properties on the block device). >> >> As in PATCH 01, "block device" could be confusing, because we use the >> term both for frontends and backends. I believe "delay-report-ns" and >> "delay-stop-ns" are the qdev properties every block device model will >> have [PATCH 11]. > > Sure. So=E2=80=A6 =E2=80=9Cblock device model=E2=80=9D, or =E2=80=9Con -d= evice=E2=80=9D? For PATCH 01, I suggested additional text that makes the meaning obvious: These are the properties "rerror" and "werror" certain block device models have. Here, you have something similar already. I think "on the block device model" would do. Or maybe "the block device model's ``delay-report-ns`` / ``delay-report-ns`` properties". >>> +# >>> +# Note that delays deliberately incurred by throttling do count >>> +# towards the operation duration. >>> +# >> >> Please use the revised syntax for introductions, like you did in PATCH >> 01: >> >> # @name: introduction, best to keep it brief, but you may continue it >> # like this if necessary. If your text need to refer to >> # arguments, it's almost certainly not brief introduction >> # anymore. >> # >> # Additional text can go here for now. >> >> I apologize for the inconvenience. We need this to eliminate certain >> syntactic ambiguities that plagued the doc generator. We'll need it >> some more for the doc inliner. > > Sure! > >>> +# @qom-path: path to the block device object in the QOM tree >>> +# >>> +# @operation: I/O operation >>> +# >>> +# @latency-ns: Ongoing duration of the operation (in nanoseconds) >>> +# >>> +# @action: Action that has been taken ("report" for "delay-report-ns" >>> +# or "stop" for "delay-stop-ns"). A "stop" action means the VM >>> +# will be stopped with the "io-hang" `RunState`, which does not >>> +# drain the block devices attached to the VM, because draining >>> +# would be counterproductive in case of a hanging I/O request. >> >> This feels less than clear. What exactly happens? My best guess: >> >> * When an operation takes longer than delay-report-ns, BLOCK_IO_DELAY is >> emitted with "action": "report" (but only once for this operation). >> >> * When an operation takes longer than delay-stop-ns, the guest is >> stopped (run state becomes io-hang), and BLOCK_IO_DELAY is emitted >> with "action": "stop". >> >> Say we continue the guest. Can the even be triggered again for this >> operation? > > No, because latency starts when the request begins, and the event (and ac= tion) happen only when that threshold is crossed. So it can be triggered once for @delay-report-ns, and once for @delay-stop-ns. Correct? In sane usage, @delay-report-ns < @delay-stop-ns. Correct? > I can try to be more clear. > >> The three possible values are ignore, report, and stop. You cover >> report and stop. Can ignore happen? > > No, it cannot. (Also by definition of `ignore` meaning to=E2=80=A6 ignore= something. So an event cannot carry this.) Try mentioning this. If the text feels worse then, don't. >> We should use ``literal`` markup for literal values. > > Sure. > > Hanna > >>> +# >>> +# @offset: Request offset in the guest disk (in bytes), if available >>> +# >>> +# @bytes: Request length >>> +# >>> +# Since: 11.2 >>> +## >>> +{ 'event': 'BLOCK_IO_DELAY', >>> + 'data': { >>> + 'qom-path': 'str', >>> + 'operation': 'IoAccountingOperation', >>> + 'latency-ns': 'uint64', >>> + 'action': 'BlockErrorAction', >>> + '*offset': 'uint64', >>> + 'bytes': 'uint64' } }