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 DF79BEFB810 for ; Tue, 24 Feb 2026 08:44:00 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vuo0W-0006DG-8V; Tue, 24 Feb 2026 03:43:04 -0500 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 1vuo0T-0006Ce-2W for qemu-devel@nongnu.org; Tue, 24 Feb 2026 03:43:01 -0500 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 1vuo0R-0006Nl-1E for qemu-devel@nongnu.org; Tue, 24 Feb 2026 03:43:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771922576; 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=NP0F3hHDXEGmveKxj/AudgtlRQuzFBgzQWgOKdkd3+g=; b=VSqNzMivH9M2KxyH+M+Tmz1UhrMdGRGcRACsyGGAPuRJ/rl/nZ/W+F5g5YZd+TT1zVr1Ny gz3vvoT3RThybTF6kN3m1pAloTLdb9lbcG3CwLrRDJK+Y6LQWqv8xC0uDJEBQICPo8ae0X nehkHvDGkpv+wH/A+PXh2TC2FTxQsdI= 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-592-3ym2HmZ3OoOpYNK5-Nd4BQ-1; Tue, 24 Feb 2026 03:42:53 -0500 X-MC-Unique: 3ym2HmZ3OoOpYNK5-Nd4BQ-1 X-Mimecast-MFC-AGG-ID: 3ym2HmZ3OoOpYNK5-Nd4BQ_1771922572 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 BECB018005B7; Tue, 24 Feb 2026 08:42:51 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.13]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0BB7219560A2; Tue, 24 Feb 2026 08:42:51 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id A633221E692D; Tue, 24 Feb 2026 09:42:48 +0100 (CET) From: Markus Armbruster To: Zhang Chen Cc: qemu-devel , "Dr . David Alan Gilbert" , Eric Blake , "Michael S . Tsirkin" , Stefan Hajnoczi Subject: Re: [PATCH V4 4/4] qapi: examine IOThread attachment status via query-iothreads In-Reply-To: (Zhang Chen's message of "Tue, 24 Feb 2026 10:42:42 +0800") References: <20260213171622.55629-1-zhangckid@gmail.com> <20260213171622.55629-4-zhangckid@gmail.com> <87wm0bq047.fsf@pond.sub.org> Date: Tue, 24 Feb 2026 09:42:48 +0100 Message-ID: <874in65y7r.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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: -1 X-Spam_score: -0.2 X-Spam_bar: / X-Spam_report: (-0.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=1.179, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.717, 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-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 Zhang Chen writes: > On Tue, Feb 17, 2026 at 3:51=E2=80=AFPM Markus Armbruster wrote: >> >> Zhang Chen writes: >> >> > Extend the 'IOThreadInfo' structure to include attachment metrics. >> > This allows users to monitor how many devices are associated with >> > a specific IOThread and identify them by their QOM paths. >> > >> > New fields added to IOThreadInfo: >> > - @attached-cnt: An integer representing the number of devices >> > currently using this IOThread's AioContext. >> > - @attached-dev: A string containing a delimited list ("|") of >> > QOM paths for the attached devices. >> > >> > These fields are also exposed via the Human Monitor Interface (HMP) >> > command 'info iothreads' to assist with manual debugging and >> > performance tuning. >> > >> > Example QMP output: >> > { >> > "id": "iothread0", >> > "thread-id": 3134, >> > "attached-cnt": 2, >> > "attached-dev": "/machine/peripheral/blk1/virtio-backend | /machin= e/peripheral/blk0/virtio-backend", >> > ... >> > } >> > >> > Signed-off-by: Zhang Chen >> >> [...] >> >> > diff --git a/qapi/misc.json b/qapi/misc.json >> > index 1f5062df2a..ca53638684 100644 >> > --- a/qapi/misc.json >> > +++ b/qapi/misc.json >> > @@ -76,6 +76,19 @@ >> > # >> > # @thread-id: ID of the underlying host thread >> > # >> > +# @attached-cnt: The parameter is a counter indicating how many >> > +# active devices are currently associated with this iothread >> > +# (e.g. virtio-blk). In hotplug scenarios, users can >> > +# pre-allocate multiple iothread objects to serve as a persistent >> > +# thread pool. When a device is hot-unplugged, the corresponding >> > +# IOThread is released but remains available, allowing subsequent >> > +# hot-plugged devices to attach to and reuse the existing thread. >> > +# (since 11.0) >> > +# >> > +# @attached-dev: A list of QOM paths for the devices currently >> > +# associated with this IOThread, delimited by " | ". >> > +# Returns "none" if no devices are attached. (since 11.0) Does not compile: In file included from ../qapi/qapi-schema.json:66: ../qapi/misc.json:90:49: Use two spaces between sentences If this not the end of a sentence, please report a bug. This error has been in master for almost three months. Is your tree that far behind? >> >> QAPI schema design maxim: do not encode structured data as strings. >> @attached-devs should be an array of QOM paths instead. > > OK, will fix in next version. Thanks! >> Unless I misunderstand your docs, @attached-cnt is the number of QOM >> paths in @attached-dev, i.e. @attached-dev is redundant. If this is the >> case, drop it. If it isn't, educate me :) > > As Stefan's comments, I try to address more specific needs: > https://mail.gnu.org/archive/html/qemu-devel/2026-02/msg01892.html As far as I can tell, Stefan asked for the QOM paths of attached devices. @attached-dev provides it. Good. Why have @attached-cnt as well? >> We generally avoid abbreviations in the QAPI schema: @attached-count, >> @attached-devices. >> >> > +# >> > # @poll-max-ns: maximum polling time in ns, 0 means polling is >> > # disabled (since 2.9) >> > # >> > @@ -93,6 +106,8 @@ >> > { 'struct': 'IOThreadInfo', >> > 'data': {'id': 'str', >> > 'thread-id': 'int', >> > + 'attached-cnt': 'int', >> > + 'attached-dev': 'str', >> > 'poll-max-ns': 'int', >> > 'poll-grow': 'int', >> > 'poll-shrink': 'int', >> > @@ -118,6 +133,8 @@ >> > # { >> > # "id":"iothread0", >> > # "thread-id":3134, >> > +# "attached-cnt":2, >> > +# "attached-dev":/machine/peripheral/blk1/virtio-back= end | /machine/peripheral/blk0/virtio-backend, >> >> Once again, the example is syntactically incorrect (the value lacks >> double quotes), and once again I recommend to create example I/O by >> actually running a test. Getting tired of this, to be frank. > > Sorry for that again. Will fix in next version. > And I tested this series before send the mail like this: > > (qemu) info iothreads > iothread2: > thread_id=3D434428 > attached-cnt=3D0 > attached-dev=3Dnone > poll-max-ns=3D32768 > poll-grow=3D0 > poll-shrink=3D0 > aio-max-batch=3D0 > iothread1: > thread_id=3D434427 > attached-cnt=3D2 > attached-dev=3D/machine/peripheral/blk1/virtio-backend | > /machine/peripheral/blk0/virtio-backend > poll-max-ns=3D32768 > poll-grow=3D0 > poll-shrink=3D0 > aio-max-batch=3D0 You can manually test QMP like this: $ qemu-system-x86_64 -S -display none -chardev socket,id=3Dqmp,path=3Dt= est-qmp,server=3Don,wait=3Doff -mon mode=3Dcontrol,chardev=3Dqmp -object io= thread,id=3Diot0 In another terminal: $ socat "READLINE,history=3D$HOME/.qmp_history,prompt=3DQMP> " UNIX-CON= NECT:test-qmp=20 {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 10}, "p= ackage": "v10.2.0-1533-g627cf8d1ed-dirty"}, "capabilities": ["oob"]}} QMP> {"execute": "qmp_capabilities", "arguments": {"enable": ["oob"]}} {"return": {}} QMP> {"execute": "query-iothreads"} {"return": [{"poll-shrink": 0, "thread-id": 2140323, "aio-max-batch": 0= , "attached-dev": "none", "poll-grow": 0, "attached-cnt": 0, "poll-max-ns":= 32768, "id": "iot0"}]} QMP> {"execute": "quit"} {"timestamp": {"seconds": 1771922506, "microseconds": 801687}, "event":= "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}} {"return": {}} >> > # "poll-max-ns":32768, >> > # "poll-grow":0, >> > # "poll-shrink":0, >> > @@ -126,6 +143,8 @@ >> > # { >> > # "id":"iothread1", >> > # "thread-id":3135, >> > +# "attached-cnt":1, >> > +# "attached-dev":/machine/peripheral/blk3/virtio-back= end, >> >> Likewise. > > Thanks > Chen > >> >> > # "poll-max-ns":32768, >> > # "poll-grow":0, >> > # "poll-shrink":0, >>