From: Christoph Hellwig <hch@lst.de>
To: Asias He <asias@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Tejun Heo <tj@kernel.org>, Shaohua Li <shli@kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path
Date: Mon, 6 Aug 2012 17:17:31 +0200 [thread overview]
Message-ID: <20120806151731.GA23220@lst.de> (raw)
In-Reply-To: <501A2178.3000906@redhat.com>
On Thu, Aug 02, 2012 at 02:43:04PM +0800, Asias He wrote:
>> Even if it has a payload waiting is highly suboptimal and it should
>> use a non-blocking sequencing like it is done in the request layer.
>
> So, for REQ_FLUSH, what we need is that send out the VIRTIO_BLK_T_FLUSH and
> not to wait.
If it's REQ_FLUSH without data a VIRTIO_BLK_T_FLUSH should be sent out only,
if it's a REQ_FLUSH that has data a VIRTIO_BLK_T_FLUSH should be sent out,
but instead of waiting for it to finish the I/O completion handler should
then submit the actual write.
> We still need to wait until the actual write is finished here?
> Like,
>
> REQ_FUA is emulated by:
> 1. Send the actual write
> 2. Wait until the actual write is finished
> 3. Send VIRTIO_BLK_T_FLUSH to device
> 4. Signal the end of the write to upper layer
Remove step 2 and run step 3 from the I/O completion handler.
next prev parent reply other threads:[~2012-08-06 15:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-02 6:25 [PATCH V5 0/4] Improve virtio-blk performance Asias He
2012-08-02 6:25 ` [PATCH V5 1/4] block: Introduce __blk_segment_map_sg() helper Asias He
2012-08-02 6:25 ` [PATCH V5 2/4] block: Add blk_bio_map_sg() helper Asias He
2012-08-02 6:25 ` [PATCH V5 3/4] virtio-blk: Add bio-based IO path for virtio-blk Asias He
2012-08-02 22:28 ` Michael S. Tsirkin
2012-08-03 7:11 ` Asias He
2012-08-02 6:25 ` [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path Asias He
2012-08-02 6:27 ` Christoph Hellwig
2012-08-02 6:43 ` Asias He
2012-08-06 15:17 ` Christoph Hellwig [this message]
2012-08-07 8:50 ` Asias He
2012-08-02 21:40 ` [PATCH V5 0/4] Improve virtio-blk performance Jens Axboe
2012-08-03 7:08 ` Asias He
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