RE: [PATCH RFC] bonding: rate-limit bonding driver inspect messages

Praveen Kannoju
2024-02-17T12:39:57Z

> -----Original Message-----
> From: Hangbin Liu <liuhangbin@gmail.com>
> Sent: 16 February 2024 02:33 PM
> To: Praveen Kannoju <praveen.kannoju@oracle.com>
> Cc: j.vosburgh@gmail.com; andy@greyhouse.net; davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Rajesh Sivaramasubramaniom
> <rajesh.sivaramasubramaniom@oracle.com>; Rama Nichanamatlu <rama.nichanamatlu@oracle.com>; Manjunath Patil
> <manjunath.b.patil@oracle.com>
> Subject: Re: [PATCH RFC] bonding: rate-limit bonding driver inspect messages
>
> On Thu, Feb 15, 2024 at 10:55:54PM +0530, Praveen Kumar Kannoju wrote:
> > Rate limit bond driver log messages, to prevent a log flood in a
> > run-away situation, e.g couldn't get rtnl lock. Message flood leads to
> > instability of system and loss of other crucial messages.
>
> Hi Praveen,
>
> The patch looks good to me. But would you please help explain why these
> slave_info() are chosen under net_ratelimit?
>
> Thanks
> Hangbin

Thank you, Hangbin.

The routine bond_mii_monitor() periodically inspects the slave carrier state in order to detect for state changes, on a state change internally records it and does the state change action.

Parked-to-Parked state changes goes through transient state. As an example for Up to Down, BOND_LINK_UP to BOND_LINK_DOWN, is thru BOND_LINK_FAIL. In order to attain next parked state or transient state bond needs rtnl mutex. If in a situation it cannot get it, a state change wouldn't happen. In order to achieve a state change as quickly as possible bond_mii_monitor() reschedules itself to come around after 1 msec. And every single come around reinspects the link and sees a state change compared to its internally recorded, which in reality internal state could be not changed earlier as failed to get rtnl lock, and throws again log indicating it sees a state change. If attaining rtnl mutex take long say hypothetical 5 secs, then bond logs 5000 state change message. 1 message at every 1 msec.

And in production environments we have seen bond taking long to achieve a state as someone else holding rtnl. Many processes do get rtnl lock. As an example we can see eth drivers. They hold rtnl mutex for the entire duration while performing a fault recovery. There are many such scenarios.

This patch doesn't change -how- bond functions. It only simply limits this kind of log flood.

-
Praveen.
> >
> > v2: Use exising net_ratelimit() instead of introducing new rate-limit
> > parameter.
> >
> > Signed-off-by: Praveen Kumar Kannoju <praveen.kannoju@oracle.com>
> > ---
> > drivers/net/bonding/bond_main.c | 36
> > ++++++++++++++++++++----------------
> > 1 file changed, 20 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/net/bonding/bond_main.c
> > b/drivers/net/bonding/bond_main.c index 4e0600c..e92eba1 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -2610,12 +2610,13 @@ static int bond_miimon_inspect(struct bonding *bond)
> > commit++;
> > slave->delay = bond->params.downdelay;
> > if (slave->delay) {
> > - slave_info(bond->dev, slave->dev, "link status down for %sinterface, disabling it in %d ms\n",
> > - (BOND_MODE(bond) ==
> > - BOND_MODE_ACTIVEBACKUP) ?
> > - (bond_is_active_slave(slave) ?
> > - "active " : "backup ") : "",
> > - bond->params.downdelay * bond->params.miimon);
> > + if (net_ratelimit())
> > + slave_info(bond->dev, slave->dev, "link status down for %sinterface, disabling it in %d ms\n",
> > + (BOND_MODE(bond) ==
> > + BOND_MODE_ACTIVEBACKUP) ?
> > + (bond_is_active_slave(slave) ?
> > + "active " : "backup ") : "",
> > + bond->params.downdelay * bond->params.miimon);
> > }
> > fallthrough;
> > case BOND_LINK_FAIL:
> > @@ -2623,9 +2624,10 @@ static int bond_miimon_inspect(struct bonding *bond)
> > /* recovered before downdelay expired */
> > bond_propose_link_state(slave, BOND_LINK_UP);
> > slave->last_link_up = jiffies;
> > - slave_info(bond->dev, slave->dev, "link status up again after %d ms\n",
> > - (bond->params.downdelay - slave->delay) *
> > - bond->params.miimon);
> > + if (net_ratelimit())
> > + slave_info(bond->dev, slave->dev, "link status up again after %d ms\n",
> > + (bond->params.downdelay - slave->delay) *
> > + bond->params.miimon);
> > commit++;
> > continue;
> > }
> > @@ -2648,18 +2650,20 @@ static int bond_miimon_inspect(struct bonding *bond)
> > slave->delay = bond->params.updelay;
> >
> > if (slave->delay) {
> > - slave_info(bond->dev, slave->dev, "link status up, enabling it in %d ms\n",
> > - ignore_updelay ? 0 :
> > - bond->params.updelay *
> > - bond->params.miimon);
> > + if (net_ratelimit())
> > + slave_info(bond->dev, slave->dev, "link status up, enabling it in %d ms\n",
> > + ignore_updelay ? 0 :
> > + bond->params.updelay *
> > + bond->params.miimon);
> > }
> > fallthrough;
> > case BOND_LINK_BACK:
> > if (!link_state) {
> > bond_propose_link_state(slave, BOND_LINK_DOWN);
> > - slave_info(bond->dev, slave->dev, "link status down again after %d ms\n",
> > - (bond->params.updelay - slave->delay) *
> > - bond->params.miimon);
> > + if (net_ratelimit())
> > + slave_info(bond->dev, slave->dev, "link status down again after %d ms\n",
> > + (bond->params.updelay - slave->delay) *
> > + bond->params.miimon);
> > commit++;
> > continue;
> > }
> > --
> > 1.8.3.1
> >