linux-kernel - RE: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle connection timer

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Date:   Tue, 15 Aug 2017 00:10:56 +0000
From:   Long Li <longli@...rosoft.com>
To:     Tom Talpey <ttalpey@...rosoft.com>,
        Steve French <sfrench@...ba.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle connection
 timer



> -----Original Message-----
> From: Tom Talpey
> Sent: Monday, August 14, 2017 4:42 PM
> To: Long Li <longli@...rosoft.com>; Steve French <sfrench@...ba.org>;
> linux-cifs@...r.kernel.org; samba-technical@...ts.samba.org; linux-
> kernel@...r.kernel.org
> Subject: RE: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle connection
> timer
> 
> > -----Original Message-----
> > From: linux-cifs-owner@...r.kernel.org [mailto:linux-cifs-
> > owner@...r.kernel.org] On Behalf Of Long Li
> > Sent: Monday, August 14, 2017 7:30 PM
> > To: Tom Talpey <ttalpey@...rosoft.com>; Steve French
> > <sfrench@...ba.org>; linux-cifs@...r.kernel.org;
> > samba-technical@...ts.samba.org; linux- kernel@...r.kernel.org
> > Subject: RE: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle
> > connection timer
> >
> > [This sender failed our fraud detection checks and may not be who they
> > appear to be. Learn about spoofing at
> > http://aka.ms/LearnAboutSpoofing]
> >
> > > -----Original Message-----
> > > From: Tom Talpey
> > > Sent: Monday, August 14, 2017 2:12 PM
> > > To: Long Li <longli@...rosoft.com>; Steve French
> > > <sfrench@...ba.org>; linux-cifs@...r.kernel.org;
> > > samba-technical@...ts.samba.org; linux- kernel@...r.kernel.org
> > > Cc: Long Li <longli@...rosoft.com>
> > > Subject: RE: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle
> > > connection timer
> > >
> > > > -----Original Message-----
> > > > From: linux-cifs-owner@...r.kernel.org [mailto:linux-cifs-
> > > > owner@...r.kernel.org] On Behalf Of Long Li
> > > > Sent: Wednesday, August 2, 2017 4:11 PM
> > > > To: Steve French <sfrench@...ba.org>; linux-cifs@...r.kernel.org;
> > > > samba- technical@...ts.samba.org; linux-kernel@...r.kernel.org
> > > > Cc: Long Li <longli@...rosoft.com>
> > > > Subject: [[PATCH v1] 25/37] [CIFS] SMBD: Support SMBD idle
> > > > connection timer
> > > >
> > > > +static int keep_alive_interval = 120;
> > >
> > > This is the recommended value, but not the only possibility.
> > >
> > > > @@ -1348,6 +1369,10 @@ struct cifs_rdma_info*
> > > cifs_create_rdma_session(
> > > >         init_waitqueue_head(&info->wait_send_queue);
> > > >         init_waitqueue_head(&info->wait_reassembly_queue);
> > > >
> > > > +       INIT_DELAYED_WORK(&info->idle_timer_work,
> > > idle_connection_timer);
> > > > +       schedule_delayed_work(&info->idle_timer_work,
> > > > +               info->keep_alive_interval*HZ);
> > > > +
> > >
> > > This initialization is ok, but the timer should be rescheduled
> > > (extended) any time any packet is sent. There is no need to perform
> > > keepalives on an active SMB Direct connection.
> >
> > My feeling is that rescheduling on a work queue for every packet is
> > sent is not efficient, especially under heavy conditions.
> 
> That's not what I was suggesting. Cant the timer simply be re-extended to
> the 120-second interval? I.e. on an active connection, it will never fire
> because it's always advancing.
> 
> As defined here, it will go off and send a keepalive every 120 seconds. The
> idle_connection_timer() routine unconditionally sends it.
> 
> >
> > Firing it every 120 seconds doesn't seem to be big waste and may
> > actually save some CPU.
> 
> Firing the timer, no big deal. Sending the packets and requiring the peer to
> process them too, disagree.

Fair enough. I will fix the code to modify delayed work instead of firing every 120 seconds.

> 
> Tom.