From: Christoph Hellwig <hch@lst.de>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@lst.de>, Jason Wang <jasowang@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, Jens Axboe <axboe@kernel.dk>,
slp@redhat.com, sgarzare@redhat.com,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 3/3] virtio_blk: implement blk_mq_ops->poll()
Date: Mon, 24 May 2021 16:59:28 +0200 [thread overview]
Message-ID: <20210524145928.GA3873@lst.de> (raw)
In-Reply-To: <20210520141305.355961-4-stefanha@redhat.com>
On Thu, May 20, 2021 at 03:13:05PM +0100, Stefan Hajnoczi wrote:
> Possible drawbacks of this approach:
>
> - Hardware virtio_blk implementations may find virtqueue_disable_cb()
> expensive since it requires DMA. If such devices become popular then
> the virtio_blk driver could use a similar approach to NVMe when
> VIRTIO_F_ACCESS_PLATFORM is detected in the future.
>
> - If a blk_poll() thread is descheduled it not only hurts polling
> performance but also delays completion of non-REQ_HIPRI requests on
> that virtqueue since vq notifications are disabled.
Yes, I think this is a dangerous configuration. What argument exists
again just using dedicated poll queues?
next prev parent reply other threads:[~2021-05-24 15:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 14:13 [PATCH 0/3] virtio_blk: blk-mq io_poll support Stefan Hajnoczi
2021-05-20 14:13 ` [PATCH 1/3] virtio: add virtioqueue_more_used() Stefan Hajnoczi
2021-05-25 2:23 ` Jason Wang
2021-05-25 8:48 ` Stefan Hajnoczi
2021-05-20 14:13 ` [PATCH 2/3] virtio_blk: avoid repeating vblk->vqs[qid] Stefan Hajnoczi
2021-05-25 2:25 ` Jason Wang
2021-05-20 14:13 ` [PATCH 3/3] virtio_blk: implement blk_mq_ops->poll() Stefan Hajnoczi
2021-05-24 14:59 ` Christoph Hellwig [this message]
2021-05-25 7:22 ` Paolo Bonzini
2021-05-25 7:38 ` Ming Lei
2021-05-25 8:06 ` Paolo Bonzini
2021-05-25 13:20 ` Stefan Hajnoczi
2021-05-25 13:19 ` Stefan Hajnoczi
2021-05-25 3:21 ` Jason Wang
2021-05-25 8:59 ` Stefan Hajnoczi
2021-05-27 5:48 ` Jason Wang
2021-06-03 15:24 ` Stefan Hajnoczi
2021-05-27 2:44 ` Ming Lei
2021-06-03 15:12 ` Stefan Hajnoczi
2021-06-03 15:30 ` [PATCH 0/3] virtio_blk: blk-mq io_poll support Stefan Hajnoczi
2021-06-16 7:43 ` Christoph Hellwig
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