From: Trond Myklebust <trondmy@primarydata.com>
To: "bfields@fieldses.org" <bfields@fieldses.org>,
"tj@kernel.org" <tj@kernel.org>,
"jlayton@poochiereds.net" <jlayton@poochiereds.net>
Cc: "bhaktipriya96@gmail.com" <bhaktipriya96@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v2] fs/nfsd/nfs4callback: Remove deprecated create_singlethread_workqueue
Date: Wed, 9 Nov 2016 15:08:52 +0000 [thread overview]
Message-ID: <1478704129.15658.1.camel@primarydata.com> (raw)
In-Reply-To: <1478697488.7930.7.camel@poochiereds.net>
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WARNING: multiple messages have this Message-ID (diff)
From: Trond Myklebust <trondmy@primarydata.com>
To: "bfields@fieldses.org" <bfields@fieldses.org>,
"tj@kernel.org" <tj@kernel.org>,
"jlayton@poochiereds.net" <jlayton@poochiereds.net>
Cc: "bhaktipriya96@gmail.com" <bhaktipriya96@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v2] fs/nfsd/nfs4callback: Remove deprecated create_singlethread_workqueue
Date: Wed, 9 Nov 2016 15:08:52 +0000 [thread overview]
Message-ID: <1478704129.15658.1.camel@primarydata.com> (raw)
In-Reply-To: <1478697488.7930.7.camel@poochiereds.net>
On Wed, 2016-11-09 at 08:18 -0500, Jeff Layton wrote:
> On Tue, 2016-11-08 at 20:27 -0500, J. Bruce Fields wrote:
> >
> > On Tue, Nov 08, 2016 at 05:52:21PM -0500, Tejun Heo wrote:
> > >
> > >
> > > Hello, Bruce.
> > >
> > > On Tue, Nov 08, 2016 at 04:39:11PM -0500, J. Bruce Fields wrote:
> > > >
> > > >
> > > > Apologies, just cleaning out old mail and finding some I should
> > > > have
> > > > responded to long ago:
> > > >
> > > > On Wed, Aug 31, 2016 at 02:23:48AM +0530, Bhaktipriya Shridhar
> > > > wrote:
> > > > >
> > > > >
> > > > > The workqueue "callback_wq" queues a single work item &cb-
> > > > > >cb_work per
> > > > > nfsd4_callback instance and thus, it doesn't require
> > > > > execution ordering.
> > > >
> > > > What's "execution ordering"?
> > > >
>
> AIUI, it means that jobs are always run in the order queued and are
> serialized.
>
> >
> > >
> > > >
> > > > We definitely do depend on the fact that at most one of these
> > > > is running
> > > > at a time.
> > >
>
> We do?
>
> >
> > >
> > > If there can be multiple cb's and thus cb->cb_work's per
> > > callback_wq,
> > > it'd need explicit ordering. Is that the case?
> >
>
> These are basically client RPC tasks, and the cb_work just handles
> the
> submission into the client RPC state machine. Just because we're
> running
> several callbacks at the same time doesn't mean that they need to be
> strictly ordered. The client state machine can certainly handle
> running
> these in parallel.
>
> >
> > Yes, there can be multiple cb_work's.
> >
>
> Yes, but each is effectively a separate work unit. I see no reason
> why
> we'd need to order them at all.
>
There needs to be serialisation at the session level (i.e. the
callbacks have to respect the slot limits set by the client) however
there shouldn’t be a need for serialisation at the RPC level.
Cheers
Trond
next prev parent reply other threads:[~2016-11-09 15:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 20:53 [PATCH v2] fs/nfsd/nfs4callback: Remove deprecated create_singlethread_workqueue Bhaktipriya Shridhar
2016-08-30 21:07 ` Jeff Layton
2016-08-31 14:39 ` Tejun Heo
2016-08-31 15:01 ` Jeff Layton
2016-11-08 21:39 ` J. Bruce Fields
2016-11-08 22:52 ` Tejun Heo
2016-11-09 1:27 ` J. Bruce Fields
2016-11-09 13:18 ` Jeff Layton
2016-11-09 15:08 ` Trond Myklebust [this message]
2016-11-09 15:08 ` Trond Myklebust
2016-11-09 15:17 ` Jeff Layton
2016-11-09 16:27 ` J. Bruce Fields
2016-11-09 17:33 ` Jeff Layton
2016-11-09 19:47 ` J. Bruce Fields
2016-11-09 20:23 ` J. Bruce Fields
2016-11-09 22:35 ` Jeff Layton
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