From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com
Subject: Re: [Qemu-devel] [PATCH 3/3] virtio-scsi-dataplane: Use main thread BH to set BDS' aio context
Date: Fri, 13 Feb 2015 10:38:43 +0100 [thread overview]
Message-ID: <54DDC623.8000307@redhat.com> (raw)
In-Reply-To: <20150213012129.GA20581@ad.nay.redhat.com>
On 13/02/2015 02:21, Fam Zheng wrote:
>> Could you just do set_aio_context for all devices when starting
>> dataplane? For example with a new scsi_device_set_aio_context function
>> (and a new method in SCSIDeviceClass).
>>
>> Maybe I'm missing the obvious. :)
>
> Per VQ IOThread stills needs it, in the case that guest switches the VQ of a
> disk on the fly.
Per VQ iothread is far away though. Multiqueue aims at parallelizing
accesses *to the same disk from different CPUs*, not at parallelizing
accesses to different disks. As long as bdrv_set_aio_context does
bdrv_drain_all, something has to change for multiqueue dataplane: either
stop using bdrv_set_aio_context, or stop doing bdrv_drain_all.
In either case, the changes are large enough that we shouldn't code for
a case that doesn't exist yet.
In addition, making the code more similar for virtio-blk and virtio-scsi
dataplane is good, because the same changes can apply to both in the future.
Paolo
next prev parent reply other threads:[~2015-02-13 9:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-12 5:20 [Qemu-devel] [PATCH 0/3] virtio-scsi: Fix unsafe bdrv_set_aio_context calls Fam Zheng
2015-02-12 5:21 ` [Qemu-devel] [PATCH 1/3] block: Forbid bdrv_set_aio_context outside BQL Fam Zheng
2015-02-13 13:10 ` Paolo Bonzini
2015-03-10 13:34 ` Stefan Hajnoczi
2015-02-12 5:21 ` [Qemu-devel] [PATCH 2/3] virtio-scsi: Deduplicate cmd queue handling code of dataplane Fam Zheng
2015-02-12 5:21 ` [Qemu-devel] [PATCH 3/3] virtio-scsi-dataplane: Use main thread BH to set BDS' aio context Fam Zheng
2015-02-12 14:29 ` Paolo Bonzini
2015-02-13 1:21 ` Fam Zheng
2015-02-13 9:38 ` Paolo Bonzini [this message]
2015-02-13 10:29 ` Fam Zheng
2015-02-13 10:38 ` Paolo Bonzini
2015-02-13 12:42 ` Fam Zheng
2015-02-13 13:12 ` Paolo Bonzini
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