From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
kvm@vger.kernel.org, rusty@rustcorp.com.au, jasowang@redhat.com,
virtualization@lists.linux-foundation.org,
Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
target-devel <target-devel@vger.kernel.org>
Subject: Re: [PATCH 5/5] virtio-scsi: introduce multiqueue support
Date: Tue, 04 Sep 2012 13:18:31 +0200 [thread overview]
Message-ID: <5045E387.4030103@redhat.com> (raw)
In-Reply-To: <20120904110905.GA9119@redhat.com>
Il 04/09/2012 13:09, Michael S. Tsirkin ha scritto:
>> > queuecommand on CPU #0 queuecommand #2 on CPU #1
>> > --------------------------------------------------------------
>> > atomic_inc_return(...) == 1
>> > atomic_inc_return(...) == 2
>> > virtscsi_queuecommand to queue #1
>> > tgt->req_vq = queue #0
>> > virtscsi_queuecommand to queue #0
>> >
>> > then two requests are issued to different queues without a quiescent
>> > point in the middle.
> What happens then? Does this break correctness?
Yes, requests to the same target should be processed in FIFO order, or
you have things like a flush issued before the write it was supposed to
flush. This is why I can only change the queue when there is no request
pending.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-scsi@vger.kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
target-devel <target-devel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 5/5] virtio-scsi: introduce multiqueue support
Date: Tue, 04 Sep 2012 13:18:31 +0200 [thread overview]
Message-ID: <5045E387.4030103@redhat.com> (raw)
In-Reply-To: <20120904110905.GA9119@redhat.com>
Il 04/09/2012 13:09, Michael S. Tsirkin ha scritto:
>> > queuecommand on CPU #0 queuecommand #2 on CPU #1
>> > --------------------------------------------------------------
>> > atomic_inc_return(...) == 1
>> > atomic_inc_return(...) == 2
>> > virtscsi_queuecommand to queue #1
>> > tgt->req_vq = queue #0
>> > virtscsi_queuecommand to queue #0
>> >
>> > then two requests are issued to different queues without a quiescent
>> > point in the middle.
> What happens then? Does this break correctness?
Yes, requests to the same target should be processed in FIFO order, or
you have things like a flush issued before the write it was supposed to
flush. This is why I can only change the queue when there is no request
pending.
Paolo
next prev parent reply other threads:[~2012-09-04 11:18 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-28 11:54 [PATCH 0/5] Multiqueue virtio-scsi Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 1/5] virtio-ring: move queue_index to vring_virtqueue Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-29 7:54 ` Jason Wang
2012-08-29 7:54 ` Jason Wang
2012-09-05 23:32 ` Rusty Russell
2012-09-05 23:32 ` Rusty Russell
2012-08-28 11:54 ` [PATCH 2/5] virtio: introduce an API to set affinity for a virtqueue Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-09-05 23:32 ` Rusty Russell
2012-09-05 23:32 ` Rusty Russell
2012-08-28 11:54 ` [PATCH 3/5] virtio-scsi: allocate target pointers in a separate memory block Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 14:07 ` Sasha Levin
2012-08-28 14:07 ` Sasha Levin
2012-08-28 14:25 ` Paolo Bonzini
2012-08-28 14:25 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 4/5] virtio-scsi: pass struct virtio_scsi to virtqueue completion function Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 5/5] virtio-scsi: introduce multiqueue support Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-09-04 2:21 ` Nicholas A. Bellinger
2012-09-04 2:21 ` Nicholas A. Bellinger
2012-09-04 6:46 ` Paolo Bonzini
2012-09-04 6:46 ` Paolo Bonzini
2012-09-04 8:46 ` Michael S. Tsirkin
2012-09-04 8:46 ` Michael S. Tsirkin
2012-09-04 10:25 ` Paolo Bonzini
2012-09-04 10:25 ` Paolo Bonzini
2012-09-04 11:09 ` Michael S. Tsirkin
2012-09-04 11:09 ` Michael S. Tsirkin
2012-09-04 11:18 ` Paolo Bonzini [this message]
2012-09-04 11:18 ` Paolo Bonzini
2012-09-04 13:35 ` Michael S. Tsirkin
2012-09-04 13:35 ` Michael S. Tsirkin
2012-09-04 13:45 ` Paolo Bonzini
2012-09-04 13:45 ` Paolo Bonzini
2012-09-04 14:19 ` Michael S. Tsirkin
2012-09-04 14:19 ` Michael S. Tsirkin
2012-09-04 14:25 ` Paolo Bonzini
2012-09-04 14:25 ` Paolo Bonzini
2012-09-04 20:11 ` Nicholas A. Bellinger
2012-09-04 20:11 ` Nicholas A. Bellinger
2012-09-05 7:03 ` Paolo Bonzini
2012-09-05 7:03 ` Paolo Bonzini
2012-09-04 12:48 ` Michael S. Tsirkin
2012-09-04 12:48 ` Michael S. Tsirkin
2012-09-04 13:49 ` Paolo Bonzini
2012-09-04 13:49 ` Paolo Bonzini
2012-09-04 14:21 ` Michael S. Tsirkin
2012-09-04 14:21 ` Michael S. Tsirkin
2012-09-04 14:30 ` Paolo Bonzini
2012-09-04 14:30 ` Paolo Bonzini
2012-09-04 14:41 ` Michael S. Tsirkin
2012-09-04 14:41 ` Michael S. Tsirkin
2012-09-04 14:47 ` Michael S. Tsirkin
2012-09-04 14:47 ` Michael S. Tsirkin
2012-09-04 14:55 ` Paolo Bonzini
2012-09-04 14:55 ` Paolo Bonzini
2012-09-04 15:03 ` Michael S. Tsirkin
2012-09-04 15:03 ` Michael S. Tsirkin
2012-08-30 7:13 ` [PATCH 0/5] Multiqueue virtio-scsi Stefan Hajnoczi
2012-08-30 7:13 ` Stefan Hajnoczi
2012-08-30 14:53 ` Michael S. Tsirkin
2012-08-30 14:53 ` Michael S. Tsirkin
2012-08-30 15:45 ` Paolo Bonzini
2012-08-30 15:45 ` Paolo Bonzini
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