From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Artem Savkov <asavkov@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
"David S. Miller" <davem@davemloft.net>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/2] net: make tcp keepalive timer upper bound
Date: Fri, 6 May 2022 09:24:10 -0700 [thread overview]
Message-ID: <20220506162410.b5wkq4ybsiut4rzu@treble> (raw)
In-Reply-To: <YnTCjFE2+/JEgglV@samus.usersys.redhat.com>
On Fri, May 06, 2022 at 08:39:08AM +0200, Artem Savkov wrote:
> On Thu, May 05, 2022 at 10:56:54AM -0700, Josh Poimboeuf wrote:
> > On Thu, May 05, 2022 at 03:18:11PM +0200, Artem Savkov wrote:
> > > Make sure TCP keepalive timer does not expire late. Switching to upper
> > > bound timers means it can fire off early but in case of keepalive
> > > tcp_keepalive_timer() handler checks elapsed time and resets the timer
> > > if it was triggered early. This results in timer "cascading" to a
> > > higher precision and being just a couple of milliseconds off it's
> > > original mark.
> > > This adds minimal overhead as keepalive timers are never re-armed and
> > > are usually quite long.
> > >
> > > Signed-off-by: Artem Savkov <asavkov@redhat.com>
> > > ---
> > > net/ipv4/inet_connection_sock.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> > > index 1e5b53c2bb26..bb2dbfb6f5b5 100644
> > > --- a/net/ipv4/inet_connection_sock.c
> > > +++ b/net/ipv4/inet_connection_sock.c
> > > @@ -589,7 +589,7 @@ EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
> > >
> > > void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
> > > {
> > > - sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
> > > + sk_reset_timer(sk, &sk->sk_timer, jiffies + upper_bound_timeout(len));
> > > }
> > > EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
> >
> > As I mentioned before, there might be two sides to the same coin,
> > depending on whether the keepalive is detecting vs preventing the
> > disconnect. So this might possibly fix one case, while breaking
> > another.
>
> But cascading is still there in the handler so it will fire off quite
> close to original timer in any case.
Ah, indeed it does. Sorry, I should try actually reading the patch
description next time :-/ Looks good to me.
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
--
Josh
next prev parent reply other threads:[~2022-05-06 16:24 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 11:16 [PATCH 0/2] Upper bound mode for kernel timers Artem Savkov
2022-03-23 11:16 ` [PATCH 1/2] timer: introduce upper bound timers Artem Savkov
2022-03-23 18:40 ` Josh Poimboeuf
2022-03-24 9:14 ` [PATCH v2 0/2] Upper bound mode for kernel timers Artem Savkov
2022-03-24 9:14 ` [PATCH v2 1/2] timer: introduce upper bound timers Artem Savkov
2022-03-24 9:15 ` [PATCH v2 2/2] net: make tcp keepalive timer upper bound Artem Savkov
2022-03-24 12:28 ` [PATCH 1/2] timer: introduce upper bound timers Thomas Gleixner
2022-03-24 13:54 ` Thomas Gleixner
2022-03-26 21:13 ` Thomas Gleixner
2022-03-30 8:20 ` [PATCH v3 0/2] Upper bound kernel timers Artem Savkov
2022-03-30 8:20 ` [PATCH v3 1/2] timer: add a function to adjust timeouts to be upper bound Artem Savkov
2022-03-30 13:40 ` Anna-Maria Behnsen
2022-04-02 6:55 ` Artem Savkov
2022-04-05 15:33 ` Thomas Gleixner
2022-04-07 7:52 ` [PATCH v4 0/2] Upper bound kernel timers Artem Savkov
2022-04-07 7:52 ` [PATCH v4 1/2] timer: add a function to adjust timeouts to be upper bound Artem Savkov
2022-04-08 0:37 ` Thomas Gleixner
2022-04-08 5:39 ` Josh Poimboeuf
2022-04-12 13:42 ` Artem Savkov
2022-05-05 13:18 ` [PATCH v5 0/2] Upper bound kernel timers Artem Savkov
2022-05-05 13:18 ` [PATCH v5 1/2] timer: add a function to adjust timeouts to be upper bound Artem Savkov
2022-05-05 13:18 ` [PATCH v5 2/2] net: make tcp keepalive timer " Artem Savkov
2022-05-05 17:56 ` Josh Poimboeuf
2022-05-06 6:39 ` Artem Savkov
2022-05-06 16:24 ` Josh Poimboeuf [this message]
2022-07-26 22:42 ` [PATCH v5 0/2] Upper bound kernel timers Josh Poimboeuf
2022-04-07 7:52 ` [PATCH v4 2/2] net: make tcp keepalive timer upper bound Artem Savkov
[not found] ` <Yk1i3WrcVIICAiF0@samus.usersys.redhat.com>
2022-04-07 23:26 ` [PATCH v3 1/2] timer: add a function to adjust timeouts to be " Thomas Gleixner
2022-03-30 8:20 ` [PATCH v3 2/2] net: make tcp keepalive timer " Artem Savkov
2022-04-02 3:09 ` [net] 6ef3f95797: UBSAN:shift-out-of-bounds_in_kernel/time/timer.c kernel test robot
2022-04-02 7:11 ` Artem Savkov
2022-03-30 10:28 ` [PATCH v3 0/2] Upper bound kernel timers David Laight
2022-03-25 7:38 ` [timer] d41e0719d5: UBSAN:shift-out-of-bounds_in_lib/flex_proportions.c kernel test robot
2022-03-25 19:14 ` Thomas Gleixner
2022-03-23 11:16 ` [PATCH 2/2] net: make tcp keepalive timer upper bound Artem Savkov
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