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From: Asias He <asias@redhat.com>
To: Christoph Hellwig <hch@lst.de>
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>
Subject: Re: [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path
Date: Tue, 07 Aug 2012 16:50:45 +0800	[thread overview]
Message-ID: <5020D6E5.3060504@redhat.com> (raw)
In-Reply-To: <20120806151731.GA23220@lst.de>

On 08/06/2012 11:17 PM, Christoph Hellwig wrote:
> 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.
>

Thanks for the explanation. V6 is in flight.

-- 
Asias

WARNING: multiple messages have this Message-ID (diff)
From: Asias He <asias@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-kernel@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>,
	Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Shaohua Li <shli@kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path
Date: Tue, 07 Aug 2012 16:50:45 +0800	[thread overview]
Message-ID: <5020D6E5.3060504@redhat.com> (raw)
In-Reply-To: <20120806151731.GA23220@lst.de>

On 08/06/2012 11:17 PM, Christoph Hellwig wrote:
> 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.
>

Thanks for the explanation. V6 is in flight.

-- 
Asias

  reply	other threads:[~2012-08-07  8:50 UTC|newest]

Thread overview: 26+ 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 ` 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   ` 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   ` 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  6:25   ` Asias He
2012-08-02 22:28   ` Michael S. Tsirkin
2012-08-02 22:28     ` Michael S. Tsirkin
2012-08-03  7:11     ` Asias He
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  6:25   ` Asias He
2012-08-02  6:27   ` Christoph Hellwig
2012-08-02  6:27     ` Christoph Hellwig
2012-08-02  6:43     ` Asias He
2012-08-02  6:43       ` Asias He
2012-08-06 15:17       ` Christoph Hellwig
2012-08-06 15:17         ` Christoph Hellwig
2012-08-07  8:50         ` Asias He [this message]
2012-08-07  8:50           ` Asias He
2012-08-02 21:40 ` [PATCH V5 0/4] Improve virtio-blk performance Jens Axboe
2012-08-02 21:40   ` Jens Axboe
2012-08-03  7:08   ` Asias He
2012-08-03  7:08     ` Asias He

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