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Date:   Wed, 27 Mar 2019 09:16:19 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     luferry <luferry@163.com>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Dongli Zhang <dongli.zhang@oracle.com>,
        Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] make blk_mq_map_queues more friendly for cpu topology
Message-ID: <20190327081619.GG20525@lst.de>
References: <20190325152640.48120-1-luferry@163.com> <20190326073954.GD21617@lst.de> <48ca2186.fc76.169b8fef63a.Coremail.luferry@163.com>
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On Tue, Mar 26, 2019 at 03:55:10PM +0800, luferry wrote:
> 
> 
> 
> At 2019-03-26 15:39:54, "Christoph Hellwig" <hch@lst.de> wrote:
> >Why isn't this using the automatic PCI-level affinity assignment to
> >start with?
> 
> When enable virtio-blk with multi queues but with only 2 msix-vector.
> vp_dev->per_vq_vectors will be false, vp_get_vq_affintity will return NULL directly
> so blk_mq_virtio_map_queues will fallback to blk_mq_map_queues.

What is the point of the multiqueue mode if you don't have enough
(virtual) MSI-X vectors?