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 3A14DC531E5 for ; Thu, 19 Feb 2026 22:28:28 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vtCUe-00070A-5P; Thu, 19 Feb 2026 17:27:32 -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 1vtCUc-0006zo-IA for qemu-devel@nongnu.org; Thu, 19 Feb 2026 17:27:30 -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 1vtCUa-0000nZ-S0 for qemu-devel@nongnu.org; Thu, 19 Feb 2026 17:27:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771540046; 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=5t/Mg7u3vkgLc7ynLOtN45ij2Ztgo7/QzQzyfLnzA/w=; b=A3BezREZ+3r6KER6QWyaaTDnoGzVuwbLVmX+oJj+2b+w4GmNC9oglybx+fONK+AyLDzgrB Du8cuo4Tlujb9z2EpRBo9tbgezYgmPpFNEv1zKQX9S02fkRZYoOtFdVGiyCVpohQ8lVFx2 97TwuC4q8FEQz2XnJPSD69+70G05CVU= Received: from mx-prod-mc-05.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-676-_rNta4XAODmy5UR6zgWXdw-1; Thu, 19 Feb 2026 17:27:22 -0500 X-MC-Unique: _rNta4XAODmy5UR6zgWXdw-1 X-Mimecast-MFC-AGG-ID: _rNta4XAODmy5UR6zgWXdw_1771540041 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 20ED31956080; Thu, 19 Feb 2026 22:27:20 +0000 (UTC) Received: from localhost (unknown [10.2.16.138]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9D4D9195410F; Thu, 19 Feb 2026 22:27:18 +0000 (UTC) Date: Thu, 19 Feb 2026 17:27:17 -0500 From: Stefan Hajnoczi To: Jaehoon Kim Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, pbonzini@redhat.com, fam@euphon.net, armbru@redhat.com, eblake@redhat.com, berrange@redhat.com, eduardo@habkost.net, dave@treblig.org, sw@weilnetz.de Subject: Re: [PATCH RFC v1 0/3] aio-poll: improve aio-polling efficiency Message-ID: <20260219222717.GA1011077@fedora> References: <20260113174824.464720-1-jhkim@linux.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="1yxXrd/Ttan4ZuPJ" Content-Disposition: inline In-Reply-To: <20260113174824.464720-1-jhkim@linux.ibm.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; 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=-0.045, 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=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable 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 --1yxXrd/Ttan4ZuPJ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hi Jaehoon, Following the call earlier this week I ran a single fio job to get a clearer picture of: 1. The QEMU 10.0.0 regression that prompted you to optimize AioContext polling. 2. How the poll-weight parameter affects IOPS. run rw bs numjobs iothreads iops diff v9.2.0 randread 8k 1 1 174944 3.6% v10.0.0 randread 8k 1 1 174285 3.2% baseline randread 8k 1 1 168908 0.0% w2 randread 8k 1 1 163718 -3.1% w3 randread 8k 1 1 165805 -1.8% w4 randread 8k 1 1 167388 -0.9% This time I only ran randread bs=8k iodepth=8 numjobs=1 with a single IOThread. Observations: - There might be an IOPS regression between v10.0.0 and the baseline (9ad7f544c696) that your patches apply on top of. This is different from the CPU utilization regression that you found in v9.2.0 -> v10.0.0. I will bisect it. - poll-weight=3 and 4 improve IOPS to a level that is acceptable. CPU utilization looks like this: run %usr %nice %sys %iowait %steal %irq %soft %guest %gnice %idle baseline 49.37 0.00 31.10 0.00 0.00 11.61 0.04 0.00 0.00 7.89 w2 46.24 0.00 32.61 0.00 0.00 11.84 0.10 0.00 0.00 9.21 w3 48.04 0.00 32.17 0.00 0.00 11.98 0.08 0.00 0.00 7.73 w4 48.56 0.00 31.23 0.00 0.00 11.48 0.03 0.00 0.00 8.69 poll-weight=2 is the winner at CPU utilization. I'm not sure if poll-weight=3 will produce an acceptable CPU utilization improvement for you. Do you have data or want to re-run to measure poll-weight=3? Stefan --1yxXrd/Ttan4ZuPJ Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmmXjkUACgkQnKSrs4Gr c8gCPgf/f4ZYLlkZ3Rn9Xo1lclPSpd5B9vPp6/mGmWfLeZF6YBKsELP4LowzLaqx +D0omCpDQ4/zcMN+VKMjG8IQ83A9expHDmVBq9QLKWiOgAc4Q05pYvvtbV4N4XOv Nul9kYsa8zySe8lOZ9FE+3FbpYZBeH4fZUcd4gIG2a9QvawPeNDy6HAHhN4Fegka cxlD/mtBFBew2akow++3AmyORVHyHNz25udrGAMpss6DsLX9IHxbXthsKKQPU87H vWJJulAfcsXT5UXxbUJXB5QAF3fltfjwFXF8RJImDTti+aFsz7ARm2x6X4OGDWBG 2SZBK+CK2Cpij+Ps+b7ynrAF5ahFbw== =bToP -----END PGP SIGNATURE----- --1yxXrd/Ttan4ZuPJ--