From: John Snow <jsnow@redhat.com>
To: Jeff Cody <jcody@redhat.com>
Cc: Liang Li <liliang.opensource@gmail.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
Kevin Wolf <kwolf@redhat.com>, Eric Blake <eblake@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Liang Li <liliangleo@didichuxing.com>,
Huaitong Han <huanhuaitong@didichuxing.com>
Subject: Re: [Qemu-devel] [PATCH] block/mirror: change the semantic of 'force' of block-job-cancel
Date: Tue, 30 Jan 2018 15:08:34 -0500 [thread overview]
Message-ID: <b5c53de8-64c7-41df-d0ba-009962a18b9e@redhat.com> (raw)
In-Reply-To: <20180130083532.GA31511@localhost>
On 01/30/2018 03:38 AM, Liang Li wrote:
> When doing drive mirror to a low speed shared storage, if there was heavy
> BLK IO write workload in VM after the 'ready' event, drive mirror block job
> can't be canceled immediately, it would keep running until the heavy BLK IO
> workload stopped in the VM.
>
> Because libvirt depends on block-job-cancel for block live migration, the
> current block-job-cancel has the semantic to make sure data is in sync after
> the 'ready' event. This semantic can't meet some requirement, for example,
> people may use drive mirror for realtime backup while need the ability of
> block live migration. If drive mirror can't not be cancelled immediately,
> it means block live migration need to wait, because libvirt make use drive
> mirror to implement block live migration and only one drive mirror block
> job is allowed at the same time for a give block dev.
>
> We need a new interface for 'force cancel', which could quit block job
> immediately if don't care about whether data is in sync or not.
>
> 'force' is not used by libvirt currently, to make things simple, change
> it's semantic slightly, hope it will not break some use case which need its
> original semantic.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Jeff Cody <jcody@redhat.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Max Reitz <mreitz@redhat.com>
> Cc: Eric Blake <eblake@redhat.com>
> Cc: John Snow <jsnow@redhat.com>
> Reported-by: Huaitong Han <huanhuaitong@didichuxing.com>
> Signed-off-by: Huaitong Han <huanhuaitong@didichuxing.com>
> Signed-off-by: Liang Li <liliangleo@didichuxing.com>
Just a note to JTC that this will conflict with my two series trying to
refactor jobs:
(1) [Qemu-devel] [PATCH v2 00/13] blockjob: refactor mirror_throttle
(2) [Qemu-devel] [RFC v3 00/14] blockjobs: add explicit job management
next prev parent reply other threads:[~2018-01-30 20:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 8:38 [Qemu-devel] [PATCH] block/mirror: change the semantic of 'force' of block-job-cancel Liang Li
2018-01-30 14:20 ` Eric Blake
2018-01-30 20:08 ` John Snow [this message]
2018-01-30 20:18 ` John Snow
2018-01-30 20:39 ` John Snow
-- strict thread matches above, loose matches on Subject: below --
2018-02-01 2:14 Liang Li
2018-02-01 2:19 Liang Li
2018-02-05 19:28 ` John Snow
2018-02-06 3:11 ` Liang Li
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