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Re: [Qemu-devel] [RFC v2 4/8] QAPI: new QMP command option "without-bql"
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [RFC v2 4/8] QAPI: new QMP command option "without-bql" |
Date: |
Fri, 25 Aug 2017 13:37:18 +0800 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Thu, Aug 24, 2017 at 07:37:32AM +0800, Fam Zheng wrote:
> On Wed, 08/23 18:44, Dr. David Alan Gilbert wrote:
> > * Peter Xu (address@hidden) wrote:
> > > Introducing this new parameter for QMP commands in general to mark out
> > > when the command does not need BQL. Normally QMP command executions are
> > > done with the protection of BQL in QEMU. However the truth is that not
> > > all the QMP commands require the BQL.
> > >
> > > This new parameter provides a way to allow QMP commands to run in
> > > parallel when possible, without the contention on the BQL.
> > >
> > > Since the default value of "without-bql" is still false, so now all QMP
> > > commands are still protected by BQL still.
> > >
> > > Signed-off-by: Peter Xu <address@hidden>
> >
> > We should define what a 'without-bql' command is allowed to do:
> > 'Commands that have without-bql set _may_ be called without the bql
> > being taken. They must not take the bql or any other lock that may
> > become dependent on the bql.'
Sure.
> > (Do we need to say anything about RCU?)
Could I ask how is RCU related?
> >
> > Also, 'no-bql' is shorter :-)
>
> Or rather "need-bql" that defaults to true to avoid double negative (TM) with
> "no-bql = false"?
Ok let me use "need-bql". :)
--
Peter Xu
[Qemu-devel] [RFC v2 6/8] migration: qmp: migrate_incoming don't need BQL, Peter Xu, 2017/08/23
[Qemu-devel] [RFC v2 7/8] migration: hmp: migrate_incoming don't need BQL, Peter Xu, 2017/08/23
[Qemu-devel] [RFC v2 8/8] migration: add incoming mgmt lock, Peter Xu, 2017/08/23