From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 6A8B93A6B9B for ; Mon, 20 Apr 2026 17:33:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776706441; cv=none; b=k5DeCTrw5bR2bQZ7RI2No3yH6XEo9JvzQP/QCJwFLgIa/wlb06hkI02sOVZg9/7XGjMeuWfO9yrLYAKXvaK5FSFUM0tY3mz3vNIlQjkBNkmbdNH262nFjQu5FJWdJ69liKm/4jz8lzE2Jx5m4cES0oUYWqbZIAVvStev7bOQKYA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776706441; c=relaxed/simple; bh=yXRXa49ii7EMtQpnop2c+sFR3fyXPbmJPIrsey3pv50=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=A5DLgKNWZ24WXA77Rk/3qNwhuOMRZr39waYi1sCJiUutdW1YnNWTsf0vfndVxA2hGv/HuflxMLYh7HXP+BHI4RKjbrzFpkx9tGCGZ1Rkc11ixiNWX/T21CVZoEMOxrvl+p8tBHHFZTeEPfQyeuwdO7NibA6nUuRuMl9hAMC1L9M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=RafTrwXP; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="RafTrwXP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1776706438; 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=yXRXa49ii7EMtQpnop2c+sFR3fyXPbmJPIrsey3pv50=; b=RafTrwXPy3U4tQgNYgbt7BwgQUvaDRzj8BuC71Hx90+vwIRNRvF1xf2uEO+uXH/1eCnxmG fi68YeFu0KdT5kONNK8zFW2C1Oj9nus+X69KIe6B85PX2/1+jHml7rkdmS+oUr9NxjTDzm j86BiKbDRw4GSTFem8ztioLJdsg/3GM= 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-270-cI8A8w63OKmBYpXpBmnZYg-1; Mon, 20 Apr 2026 13:33:57 -0400 X-MC-Unique: cI8A8w63OKmBYpXpBmnZYg-1 X-Mimecast-MFC-AGG-ID: cI8A8w63OKmBYpXpBmnZYg_1776706435 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 75A7118004AD; Mon, 20 Apr 2026 17:33:55 +0000 (UTC) Received: from localhost (unknown [10.44.48.35]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 531E21800370; Mon, 20 Apr 2026 17:33:54 +0000 (UTC) Date: Mon, 20 Apr 2026 13:33:52 -0400 From: Stefan Hajnoczi To: Mike Christie Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org, james.bottomley@hansenpartnership.com, virtualization@lists.linux.dev, mst@redhat.com, pbonzini@redhat.com, eperezma@redhat.com Subject: Re: [PATCH 0/4] scsi: Support devices that don't have a cmd_per_lun limit Message-ID: <20260420173352.GB405461@fedora> References: <20260417230751.117836-1-michael.christie@oracle.com> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="KaAzs6/QIPBWgyu3" Content-Disposition: inline In-Reply-To: <20260417230751.117836-1-michael.christie@oracle.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 --KaAzs6/QIPBWgyu3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Apr 17, 2026 at 05:57:20PM -0500, Mike Christie wrote: > The following patches were made over Linus's and Martin's 7.1 trees. > They fix an issue where for virtio-scsi we export a lot of non-scsi > devices but are getting throttled by the cmd_per_lun_limit too early. > For example we export 1 or more NVMe or block devices and would like > to just pass command to them in way where virtio-scsi's hw queue > limits match the physical hardware. Or in some cases we are doing > cgroup based throttling on the host side, and we don't want the guest > to block IO when the host knows we have extra bandwidth. >=20 > The patches add a new cmd_per_lun value so drivers can indicate > when to avoid tracking queueing at the device wide level. They > then rely on just the block layer hw queue limits. And the patches > convert virtio-scsi. They also fix some can_queue related issues > discovered while testing/reviewing. Hi Mike, Is there a difference between setting cmd_per_lun to U32_MAX with your patches versus setting cmd_per_lun to the virtqueue size without your patches (this can already be done today without code changes in the driver)? Thanks, Stefan --KaAzs6/QIPBWgyu3 Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmnmY4AACgkQnKSrs4Gr c8gWQggAih11OwTFLYPwIEPZH1UoehTgpAOlQUsDBxyaxZCSkkcVN/d4+9/Hbs4A dIczEZdYWOmzAHeefxcR3HUWWVU29v5ZpoeKY9eWb/JEhNujh8U6bx6GoMn3jVq4 PIfqU8p4YKZRhpRg4VR/JZbN9LEydANb53rOStyCrp8CAy+8nCvQ2gQrxHyyTeSH mSAEjLuLNGBw5tjO5SqfHkQR8WTzDLW5G3ErW+goMtDaQ6zR4ezVuq9JKn72RLAV VAVjWnRsXjgvhUVr3zzoHwdfj2fH0U7TNZ1RI9//BvC/lpzSKqsNuvdY/hxtT+8U XObCdlBmXMXApDvpnKYliXxm8MRLbA== =F1XH -----END PGP SIGNATURE----- --KaAzs6/QIPBWgyu3--