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 X-Spam-Level: X-Spam-Status: No, score=-16.1 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_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4E01C433EF for ; Sun, 12 Sep 2021 09:51:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C564610CE for ; Sun, 12 Sep 2021 09:51:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232125AbhILJwO (ORCPT ); Sun, 12 Sep 2021 05:52:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:53311 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233403AbhILJwO (ORCPT ); Sun, 12 Sep 2021 05:52:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631440259; 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=DO0lP6RjLZGuAwzVarCFdM0VM58MS0sPAfAXE13fr4c=; b=I+Om7A05TTUu8UwnL88wsFXVaz7NUw2wN8Tndm3SYinSC6f9zF7I+0rlBEh5mEr57ycn1V TCMMM79gPI+itIaHz90nv6uaCl1nhNv5hSJsI1EI6bntogB7Et5EfEGA147ZcMct87MRHb 2ggftAK+bfwQ5+citbQ6rnjrOJsLTNA= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-508-sDC2oHczO3yg_s6UW8hNxA-1; Sun, 12 Sep 2021 05:50:58 -0400 X-MC-Unique: sDC2oHczO3yg_s6UW8hNxA-1 Received: by mail-ed1-f71.google.com with SMTP id s12-20020a05640217cc00b003cde58450f1so3313405edy.9 for ; Sun, 12 Sep 2021 02:50:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=DO0lP6RjLZGuAwzVarCFdM0VM58MS0sPAfAXE13fr4c=; b=tpP41MBSr++yD8YICFTT7OHvjdnKS7nozPCkGPCIOPeAlNwdO3Fa4fwtIHNiGBvVhh n8iIA4dV8klG2eF3rlg+1FlKrx642USBB4NW64KdC2auZnvppyaPwMHRMcOzpOv+GITm XzQkokC1y0bWI/iyoIBaYXGo9EMGJf2588BhaxA+ww0TlALinfjojnXUI/XAqmHTI+pe +mTzvHoNI6Ca0yew8fDHx4eN0aU+Rbqb/CgOjPaSQKgw8TiLOtmMNopQziQdSTcOSZ9N YhtKiiwbTBVgT5jDi8cjvn5TGwxIypC2/t/nPqQ808igFdjjEmrHJzEz149O5O3Ss41O wphA== X-Gm-Message-State: AOAM530AlDF1/l66uL1qNvJYwDxq7eIUt6MPbJk3VO66m7B9NH0GP/Zu c3L5aAKSZLaP7/+oMOAiqd2NKaMVU5nzaFypAbs7DVd210sY63UfRh6S4zBH3cnCUYdHGzAATbl n0g/ofMHCoG/gVmcePaNJ7io= X-Received: by 2002:a17:906:b08e:: with SMTP id x14mr6858882ejy.40.1631440257287; Sun, 12 Sep 2021 02:50:57 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxfzYlW00EflVZRuhrUrZmzBRewk6zsNxfHiJAIwWbYcmxK42e9TZoQ8zJXVI/1VvQk7LkshA== X-Received: by 2002:a17:906:b08e:: with SMTP id x14mr6858859ejy.40.1631440257074; Sun, 12 Sep 2021 02:50:57 -0700 (PDT) Received: from redhat.com ([2.55.27.174]) by smtp.gmail.com with ESMTPSA id t5sm2048235edd.66.2021.09.12.02.50.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Sep 2021 02:50:55 -0700 (PDT) Date: Sun, 12 Sep 2021 05:50:51 -0400 From: "Michael S. Tsirkin" To: Max Gurtovoy Cc: Stefan Hajnoczi , hch@infradead.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, israelr@nvidia.com, nitzanc@nvidia.com, oren@nvidia.com, linux-block@vger.kernel.org, axboe@kernel.dk Subject: Re: [PATCH v2 1/1] virtio-blk: add num_io_queues module parameter Message-ID: <20210912054959-mutt-send-email-mst@kernel.org> References: <20210909094001-mutt-send-email-mst@kernel.org> <456e1704-67e9-aac9-a82a-44fed65dd153@nvidia.com> <20210909114029-mutt-send-email-mst@kernel.org> <20210909123035-mutt-send-email-mst@kernel.org> <0cd4ab50-1bb2-3baf-fc00-b2045e8f8eb1@nvidia.com> <20210909185525-mutt-send-email-mst@kernel.org> <9de9a43a-2d3a-493b-516e-4601778b9237@nvidia.com> <20210912050531-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, Sep 12, 2021 at 12:37:26PM +0300, Max Gurtovoy wrote: > > On 9/12/2021 12:07 PM, Michael S. Tsirkin wrote: > > On Sat, Sep 11, 2021 at 03:56:45PM +0300, Max Gurtovoy wrote: > > > On 9/10/2021 1:57 AM, Michael S. Tsirkin wrote: > > > > On Thu, Sep 09, 2021 at 07:45:42PM +0300, Max Gurtovoy wrote: > > > > > On 9/9/2021 7:31 PM, Michael S. Tsirkin wrote: > > > > > > On Thu, Sep 09, 2021 at 06:51:56PM +0300, Max Gurtovoy wrote: > > > > > > > On 9/9/2021 6:40 PM, Michael S. Tsirkin wrote: > > > > > > > > On Thu, Sep 09, 2021 at 06:37:37PM +0300, Max Gurtovoy wrote: > > > > > > > > > On 9/9/2021 4:42 PM, Michael S. Tsirkin wrote: > > > > > > > > > > On Mon, Sep 06, 2021 at 02:59:40PM +0300, Max Gurtovoy wrote: > > > > > > > > > > > On 9/6/2021 2:20 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > On Mon, Sep 06, 2021 at 01:31:32AM +0300, Max Gurtovoy wrote: > > > > > > > > > > > > > On 9/5/2021 7:02 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > > > On Thu, Sep 02, 2021 at 02:45:52PM +0100, Stefan Hajnoczi wrote: > > > > > > > > > > > > > > > On Tue, Aug 31, 2021 at 04:50:35PM +0300, Max Gurtovoy wrote: > > > > > > > > > > > > > > > > Sometimes a user would like to control the amount of IO queues to be > > > > > > > > > > > > > > > > created for a block device. For example, for limiting the memory > > > > > > > > > > > > > > > > footprint of virtio-blk devices. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Max Gurtovoy > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > changes from v1: > > > > > > > > > > > > > > > > - use param_set_uint_minmax (from Christoph) > > > > > > > > > > > > > > > > - added "Should > 0" to module description > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Note: This commit apply on top of Jens's branch for-5.15/drivers > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > drivers/block/virtio_blk.c | 20 +++++++++++++++++++- > > > > > > > > > > > > > > > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > index 4b49df2dfd23..9332fc4e9b31 100644 > > > > > > > > > > > > > > > > --- a/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > +++ b/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > @@ -24,6 +24,22 @@ > > > > > > > > > > > > > > > > /* The maximum number of sg elements that fit into a virtqueue */ > > > > > > > > > > > > > > > > #define VIRTIO_BLK_MAX_SG_ELEMS 32768 > > > > > > > > > > > > > > > > +static int virtblk_queue_count_set(const char *val, > > > > > > > > > > > > > > > > + const struct kernel_param *kp) > > > > > > > > > > > > > > > > +{ > > > > > > > > > > > > > > > > + return param_set_uint_minmax(val, kp, 1, nr_cpu_ids); > > > > > > > > > > > > > > > > +} > > > > > > > > > > > > Hmm which tree is this for? > > > > > > > > > > > I've mentioned in the note that it apply on branch for-5.15/drivers. But now > > > > > > > > > > > you can apply it on linus/master as well. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > +static const struct kernel_param_ops queue_count_ops = { > > > > > > > > > > > > > > > > + .set = virtblk_queue_count_set, > > > > > > > > > > > > > > > > + .get = param_get_uint, > > > > > > > > > > > > > > > > +}; > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > +static unsigned int num_io_queues; > > > > > > > > > > > > > > > > +module_param_cb(num_io_queues, &queue_count_ops, &num_io_queues, 0644); > > > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_queues, > > > > > > > > > > > > > > > > + "Number of IO virt queues to use for blk device. Should > 0"); > > > > > > > > > > > > better: > > > > > > > > > > > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_request_queues, > > > > > > > > > > > > + "Limit number of IO request virt queues to use for each device. 0 for now limit"); > > > > > > > > > > > You proposed it and I replied on it bellow. > > > > > > > > > > Can't say I understand 100% what you are saying. Want to send > > > > > > > > > > a description that does make sense to you but > > > > > > > > > > also reflects reality? 0 is the default so > > > > > > > > > > "should > 0" besides being ungrammatical does not seem t" > > > > > > > > > > reflect what it does ... > > > > > > > > > if you "modprobe virtio_blk" the previous behavior will happen. > > > > > > > > > > > > > > > > > > You can't "modprobe virtio_blk num_io_request_queues=0" since the minimal > > > > > > > > > value is 1. > > > > > > > > > > > > > > > > > > So your description is not reflecting the code. > > > > > > > > > > > > > > > > > > We can do: > > > > > > > > > > > > > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. Minimum value is 1 queue"); > > > > > > > > What's the default value? We should document that. > > > > > > > default value for static global variables is 0. > > > > > > > > > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to > > > > > > > use for blk device. Minimum value is 1 queue. Default and Maximum value is > > > > > > > equal to the total number of CPUs"); > > > > > > So it says it's the # of cpus but yoiu inspect it with > > > > > > sysfs and it's actually 0. Let's say that's confusing > > > > > > at the least. why not just let users set it to 0 > > > > > > and document that? > > > > > > > > > > > Setting it by the user to 0 makes no sense. > > > > > > > > > > We can say "if not set, the value equals to the total number of CPUs". > > > > the value is 0. it seems to mean "no limit". the actual # of queues is > > > > then te smaller between # of cpus and # of hardware queues. > > > > I see no reason not to allow user to set that especially if > > > > it was originally the value then user changed it > > > > and is trying to change it back. > > > I fine with that. > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. 0 value means no limitation"); > > > > > OK and the second distinction is that it's a limit on the > > number, not the actual number. It's never more than what's provided > > by the hypervisor. > > MODULE_PARM_DESC(num_io_request_queues, "Maximal number of request virt queues to use for blk device. 0 value means no limitation"); > > is that ok ? Looks ok. And then do we need to limit this to nr_cpu_ids? Setting a value that's too high seems harmless ... > > > > > The actual value of the created queues can be seen in /sys/block/vda/mq/ as > > > > > done today. > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > static int major; > > > > > > > > > > > > > > > > static DEFINE_IDA(vd_index_ida); > > > > > > > > > > > > > > > > @@ -501,7 +517,9 @@ static int init_vq(struct virtio_blk *vblk) > > > > > > > > > > > > > > > > if (err) > > > > > > > > > > > > > > > > num_vqs = 1; > > > > > > > > > > > > > > > > - num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); > > > > > > > > > > > > > > > > + num_vqs = min_t(unsigned int, > > > > > > > > > > > > > > > > + min_not_zero(num_io_queues, nr_cpu_ids), > > > > > > > > > > > > > > > > + num_vqs); > > > > > > > > > > > > > > > If you respin, please consider calling them request queues. That's the > > > > > > > > > > > > > > > terminology from the VIRTIO spec and it's nice to keep it consistent. > > > > > > > > > > > > > > > But the purpose of num_io_queues is clear, so: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Reviewed-by: Stefan Hajnoczi > > > > > > > > > > > > > > I did this: > > > > > > > > > > > > > > +static unsigned int num_io_request_queues; > > > > > > > > > > > > > > +module_param_cb(num_io_request_queues, &queue_count_ops, &num_io_request_queues, 0644); > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_request_queues, > > > > > > > > > > > > > > + "Limit number of IO request virt queues to use for each device. 0 for now limit"); > > > > > > > > > > > > > The parameter is writable and can be changed and then new devices might be > > > > > > > > > > > > > probed with new value. > > > > > > > > > > > > > > > > > > > > > > > > > > It can't be zero in the code. we can change param_set_uint_minmax args and > > > > > > > > > > > > > say that 0 says nr_cpus. > > > > > > > > > > > > > > > > > > > > > > > > > > I'm ok with the renaming but I prefer to stick to the description we gave in > > > > > > > > > > > > > V3 of this patch (and maybe enable value of 0 as mentioned above). 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Tsirkin" To: Max Gurtovoy Subject: Re: [PATCH v2 1/1] virtio-blk: add num_io_queues module parameter Message-ID: <20210912054959-mutt-send-email-mst@kernel.org> References: <20210909094001-mutt-send-email-mst@kernel.org> <456e1704-67e9-aac9-a82a-44fed65dd153@nvidia.com> <20210909114029-mutt-send-email-mst@kernel.org> <20210909123035-mutt-send-email-mst@kernel.org> <0cd4ab50-1bb2-3baf-fc00-b2045e8f8eb1@nvidia.com> <20210909185525-mutt-send-email-mst@kernel.org> <9de9a43a-2d3a-493b-516e-4601778b9237@nvidia.com> <20210912050531-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: axboe@kernel.dk, linux-block@vger.kernel.org, kvm@vger.kernel.org, israelr@nvidia.com, virtualization@lists.linux-foundation.org, hch@infradead.org, nitzanc@nvidia.com, Stefan Hajnoczi , oren@nvidia.com X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Sun, Sep 12, 2021 at 12:37:26PM +0300, Max Gurtovoy wrote: > > On 9/12/2021 12:07 PM, Michael S. Tsirkin wrote: > > On Sat, Sep 11, 2021 at 03:56:45PM +0300, Max Gurtovoy wrote: > > > On 9/10/2021 1:57 AM, Michael S. Tsirkin wrote: > > > > On Thu, Sep 09, 2021 at 07:45:42PM +0300, Max Gurtovoy wrote: > > > > > On 9/9/2021 7:31 PM, Michael S. Tsirkin wrote: > > > > > > On Thu, Sep 09, 2021 at 06:51:56PM +0300, Max Gurtovoy wrote: > > > > > > > On 9/9/2021 6:40 PM, Michael S. Tsirkin wrote: > > > > > > > > On Thu, Sep 09, 2021 at 06:37:37PM +0300, Max Gurtovoy wrote: > > > > > > > > > On 9/9/2021 4:42 PM, Michael S. Tsirkin wrote: > > > > > > > > > > On Mon, Sep 06, 2021 at 02:59:40PM +0300, Max Gurtovoy wrote: > > > > > > > > > > > On 9/6/2021 2:20 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > On Mon, Sep 06, 2021 at 01:31:32AM +0300, Max Gurtovoy wrote: > > > > > > > > > > > > > On 9/5/2021 7:02 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > > > On Thu, Sep 02, 2021 at 02:45:52PM +0100, Stefan Hajnoczi wrote: > > > > > > > > > > > > > > > On Tue, Aug 31, 2021 at 04:50:35PM +0300, Max Gurtovoy wrote: > > > > > > > > > > > > > > > > Sometimes a user would like to control the amount of IO queues to be > > > > > > > > > > > > > > > > created for a block device. For example, for limiting the memory > > > > > > > > > > > > > > > > footprint of virtio-blk devices. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Max Gurtovoy > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > changes from v1: > > > > > > > > > > > > > > > > - use param_set_uint_minmax (from Christoph) > > > > > > > > > > > > > > > > - added "Should > 0" to module description > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Note: This commit apply on top of Jens's branch for-5.15/drivers > > > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > drivers/block/virtio_blk.c | 20 +++++++++++++++++++- > > > > > > > > > > > > > > > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > index 4b49df2dfd23..9332fc4e9b31 100644 > > > > > > > > > > > > > > > > --- a/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > +++ b/drivers/block/virtio_blk.c > > > > > > > > > > > > > > > > @@ -24,6 +24,22 @@ > > > > > > > > > > > > > > > > /* The maximum number of sg elements that fit into a virtqueue */ > > > > > > > > > > > > > > > > #define VIRTIO_BLK_MAX_SG_ELEMS 32768 > > > > > > > > > > > > > > > > +static int virtblk_queue_count_set(const char *val, > > > > > > > > > > > > > > > > + const struct kernel_param *kp) > > > > > > > > > > > > > > > > +{ > > > > > > > > > > > > > > > > + return param_set_uint_minmax(val, kp, 1, nr_cpu_ids); > > > > > > > > > > > > > > > > +} > > > > > > > > > > > > Hmm which tree is this for? > > > > > > > > > > > I've mentioned in the note that it apply on branch for-5.15/drivers. But now > > > > > > > > > > > you can apply it on linus/master as well. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > +static const struct kernel_param_ops queue_count_ops = { > > > > > > > > > > > > > > > > + .set = virtblk_queue_count_set, > > > > > > > > > > > > > > > > + .get = param_get_uint, > > > > > > > > > > > > > > > > +}; > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > +static unsigned int num_io_queues; > > > > > > > > > > > > > > > > +module_param_cb(num_io_queues, &queue_count_ops, &num_io_queues, 0644); > > > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_queues, > > > > > > > > > > > > > > > > + "Number of IO virt queues to use for blk device. Should > 0"); > > > > > > > > > > > > better: > > > > > > > > > > > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_request_queues, > > > > > > > > > > > > + "Limit number of IO request virt queues to use for each device. 0 for now limit"); > > > > > > > > > > > You proposed it and I replied on it bellow. > > > > > > > > > > Can't say I understand 100% what you are saying. Want to send > > > > > > > > > > a description that does make sense to you but > > > > > > > > > > also reflects reality? 0 is the default so > > > > > > > > > > "should > 0" besides being ungrammatical does not seem t" > > > > > > > > > > reflect what it does ... > > > > > > > > > if you "modprobe virtio_blk" the previous behavior will happen. > > > > > > > > > > > > > > > > > > You can't "modprobe virtio_blk num_io_request_queues=0" since the minimal > > > > > > > > > value is 1. > > > > > > > > > > > > > > > > > > So your description is not reflecting the code. > > > > > > > > > > > > > > > > > > We can do: > > > > > > > > > > > > > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. Minimum value is 1 queue"); > > > > > > > > What's the default value? We should document that. > > > > > > > default value for static global variables is 0. > > > > > > > > > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to > > > > > > > use for blk device. Minimum value is 1 queue. Default and Maximum value is > > > > > > > equal to the total number of CPUs"); > > > > > > So it says it's the # of cpus but yoiu inspect it with > > > > > > sysfs and it's actually 0. Let's say that's confusing > > > > > > at the least. why not just let users set it to 0 > > > > > > and document that? > > > > > > > > > > > Setting it by the user to 0 makes no sense. > > > > > > > > > > We can say "if not set, the value equals to the total number of CPUs". > > > > the value is 0. it seems to mean "no limit". the actual # of queues is > > > > then te smaller between # of cpus and # of hardware queues. > > > > I see no reason not to allow user to set that especially if > > > > it was originally the value then user changed it > > > > and is trying to change it back. > > > I fine with that. > > > > > > MODULE_PARM_DESC(num_io_request_queues, "Number of request virt queues to use for blk device. 0 value means no limitation"); > > > > > OK and the second distinction is that it's a limit on the > > number, not the actual number. It's never more than what's provided > > by the hypervisor. > > MODULE_PARM_DESC(num_io_request_queues, "Maximal number of request virt queues to use for blk device. 0 value means no limitation"); > > is that ok ? Looks ok. And then do we need to limit this to nr_cpu_ids? Setting a value that's too high seems harmless ... > > > > > The actual value of the created queues can be seen in /sys/block/vda/mq/ as > > > > > done today. > > > > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > static int major; > > > > > > > > > > > > > > > > static DEFINE_IDA(vd_index_ida); > > > > > > > > > > > > > > > > @@ -501,7 +517,9 @@ static int init_vq(struct virtio_blk *vblk) > > > > > > > > > > > > > > > > if (err) > > > > > > > > > > > > > > > > num_vqs = 1; > > > > > > > > > > > > > > > > - num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); > > > > > > > > > > > > > > > > + num_vqs = min_t(unsigned int, > > > > > > > > > > > > > > > > + min_not_zero(num_io_queues, nr_cpu_ids), > > > > > > > > > > > > > > > > + num_vqs); > > > > > > > > > > > > > > > If you respin, please consider calling them request queues. That's the > > > > > > > > > > > > > > > terminology from the VIRTIO spec and it's nice to keep it consistent. > > > > > > > > > > > > > > > But the purpose of num_io_queues is clear, so: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Reviewed-by: Stefan Hajnoczi > > > > > > > > > > > > > > I did this: > > > > > > > > > > > > > > +static unsigned int num_io_request_queues; > > > > > > > > > > > > > > +module_param_cb(num_io_request_queues, &queue_count_ops, &num_io_request_queues, 0644); > > > > > > > > > > > > > > +MODULE_PARM_DESC(num_io_request_queues, > > > > > > > > > > > > > > + "Limit number of IO request virt queues to use for each device. 0 for now limit"); > > > > > > > > > > > > > The parameter is writable and can be changed and then new devices might be > > > > > > > > > > > > > probed with new value. > > > > > > > > > > > > > > > > > > > > > > > > > > It can't be zero in the code. we can change param_set_uint_minmax args and > > > > > > > > > > > > > say that 0 says nr_cpus. > > > > > > > > > > > > > > > > > > > > > > > > > > I'm ok with the renaming but I prefer to stick to the description we gave in > > > > > > > > > > > > > V3 of this patch (and maybe enable value of 0 as mentioned above). _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization