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 162BBF4BB9A for ; Wed, 25 Feb 2026 10:55:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vvCXu-0004Bx-E1; Wed, 25 Feb 2026 05:55:10 -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 1vvCXo-0004Bd-Is for qemu-devel@nongnu.org; Wed, 25 Feb 2026 05:55:08 -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 1vvCXk-0000ue-Az for qemu-devel@nongnu.org; Wed, 25 Feb 2026 05:55:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772016899; 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=ECrzQKuRTVP8rIxsh1wBi6ZL45U8oEQ4dQNbIfOE5LI=; b=aWF6v+NsAdJqA9PIG7xGhBVlvXPJYDMBSFIKHkLHCU6Y9DLOjJsWzByEhsJgrNDuP9Q1jV Y8ioa2CimEgP8JS9DUoIjdl5xgiXbEbnnXS8ojwMAT+fmPqumuuq1/X/SGTUsdl6l95xl0 +3vD73PbWfmAZkG3SySHrkOLlTJTMWo= Received: from mx-prod-mc-08.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-344-6CpSe_DfMaaqOcYkot43ZQ-1; Wed, 25 Feb 2026 05:54:57 -0500 X-MC-Unique: 6CpSe_DfMaaqOcYkot43ZQ-1 X-Mimecast-MFC-AGG-ID: 6CpSe_DfMaaqOcYkot43ZQ_1772016896 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 559FF18004A9; Wed, 25 Feb 2026 10:54:56 +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 C9D5319560A2; Wed, 25 Feb 2026 10:54:55 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 7234421E692D; Wed, 25 Feb 2026 11:54:53 +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 "Wed, 25 Feb 2026 18:29:29 +0800") References: <20260213171622.55629-1-zhangckid@gmail.com> <20260213171622.55629-4-zhangckid@gmail.com> <87wm0bq047.fsf@pond.sub.org> <874in65y7r.fsf@pond.sub.org> Date: Wed, 25 Feb 2026 11:54:53 +0100 Message-ID: <87jyw1um82.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: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 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_RPBL_BLOCKED=0.358, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.659, 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 24, 2026 at 4:42=E2=80=AFPM Markus Armbruster wrote: >> >> 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 | /mac= hine/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 persist= ent >> >> > +# thread pool. When a device is hot-unplugged, the correspond= ing >> >> > +# IOThread is released but remains available, allowing subsequ= ent >> >> > +# hot-plugged devices to attach to and reuse the existing thre= ad. >> >> > +# (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) [...] >> >> >> >> 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? >> > > Users can obtain the quantity more conveniently, avoiding the need to > count the number of @attached-dev. > If you think the @attached-cnt is redundant, I will remove it in next ver= sion. Please do. [...]