From: rcochran@linutronix.de
To: Jouni Malinen <j@w1.fi>
Cc: Richard Cochran <richardcochran@gmail.com>,
Jouni Malinen <jkmalinen@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Rik van Riel <riel@redhat.com>, Len Brown <lenb@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
George Spelvin <linux@sciencehorizons.net>,
Josh Triplett <josh@joshtriplett.org>, Chris Mason <clm@fb.com>,
Eric Dumazet <edumazet@google.com>,
rt@linutronix.de, Paul McKenney <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Arjan van de Ven <arjan@infradead.org>
Subject: Re: [PREEMPT-RT] [patch 4 14/22] timer: Switch to a non cascading wheel
Date: Wed, 17 Aug 2016 11:23:26 +0200 [thread overview]
Message-ID: <20160817092326.GB27858@linutronix.de> (raw)
In-Reply-To: <20160817090522.GA4284@w1.fi>
On Wed, Aug 17, 2016 at 12:05:22PM +0300, Jouni Malinen wrote:
> I had not realized this previously due to the test case passing, but the
> same retransmit SYN case was happening with older kernels, it just was
> done a tiny bit faster to escape that 1.0 second timeout limit.. That
> about 1.03 sec value after this kernel commit is 1.0 sec before this
> kernel commit. In other words, something in this specific kernel commit
> seems to add about 0.03 sec delay to the TCP SYN retransmission.
Yes, and this 3% increase in the timeout expiration interval is an
expected result using the new timer wheel. See the large comment at
the top of kernel/time/timer.c and the lkml discussion about this
series.
> That
> said, I realize that this is quite unlikely timeout to use for connect()
> in real world and as such, it looks simply as a side effect of a test
> case that was using way too close timing requirement in the first place.
Right, and user space should not rely on the exact timing of TCP SYN
re-transmission!
Thanks,
Richard
next prev parent reply other threads:[~2016-08-17 9:23 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-04 9:50 [patch 4 00/22] timer: Refactor the timer wheel Thomas Gleixner
2016-07-04 9:50 ` [patch 4 01/22] timer: Make pinned a timer property Thomas Gleixner
2016-07-07 8:39 ` [tip:timers/core] timers: Make 'pinned' " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 02/22] x86/apic/uv: Initialize timer as pinned Thomas Gleixner
2016-07-07 8:40 ` [tip:timers/core] timers, x86/apic/uv: Initialize the UV heartbeat " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 03/22] x86/mce: Initialize " Thomas Gleixner
2016-07-07 8:40 ` [tip:timers/core] timers, x86/mce: Initialize MCE restart " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 04/22] cpufreq/powernv: Initialize " Thomas Gleixner
2016-07-07 8:41 ` [tip:timers/core] timers, cpufreq/powernv: Initialize the gpstate " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 05/22] driver/net/ethernet/tile: Initialize " Thomas Gleixner
2016-07-07 8:41 ` [tip:timers/core] timers, driver/net/ethernet/tile: Initialize the egress " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 06/22] drivers/tty/metag_da: Initialize " Thomas Gleixner
2016-07-07 8:42 ` [tip:timers/core] timers, drivers/tty/metag_da: Initialize the poll " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 07/22] drivers/tty/mips_ejtag: Initialize " Thomas Gleixner
2016-07-07 8:42 ` [tip:timers/core] timers, drivers/tty/mips_ejtag: Initialize the poll " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 08/22] net/ipv4/inet: Initialize timers " Thomas Gleixner
2016-07-07 8:43 ` [tip:timers/core] timers, net/ipv4/inet: Initialize connection request " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 09/22] timer: Remove mod_timer_pinned Thomas Gleixner
2016-07-07 8:43 ` [tip:timers/core] timers: Remove the deprecated mod_timer_pinned() API tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 10/22] signal: Use hrtimer for sigtimedwait Thomas Gleixner
2016-07-07 8:43 ` [tip:timers/core] signals: Use hrtimer for sigtimedwait() tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 11/22] hlist: Add hlist_is_singular_node() helper Thomas Gleixner
2016-07-07 8:44 ` [tip:timers/core] " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 12/22] timer: Give a few structs and members proper names Thomas Gleixner
2016-07-07 8:44 ` [tip:timers/core] timers: " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 13/22] timer: Reduce the CPU index space to 256k Thomas Gleixner
2016-07-07 8:45 ` [tip:timers/core] timers: " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 14/22] timer: Switch to a non cascading wheel Thomas Gleixner
2016-07-07 8:45 ` [tip:timers/core] timers: Switch to a non-cascading wheel tip-bot for Thomas Gleixner
2016-08-11 15:21 ` [patch 4 14/22] timer: Switch to a non cascading wheel Jouni Malinen
2016-08-11 20:25 ` [PREEMPT-RT] " rcochran
2016-08-13 9:12 ` Jouni Malinen
2016-08-16 9:46 ` Richard Cochran
2016-08-16 14:35 ` Eric Dumazet
2016-08-17 9:05 ` Jouni Malinen
2016-08-17 9:23 ` rcochran [this message]
2016-08-12 17:50 ` Rik van Riel
2016-08-12 19:14 ` Paul E. McKenney
2016-08-16 8:55 ` Richard Cochran
2016-08-16 7:57 ` Richard Cochran
2016-07-04 9:50 ` [patch 4 15/22] timer: Remove slack leftovers Thomas Gleixner
2016-07-07 8:46 ` [tip:timers/core] timers: Remove set_timer_slack() leftovers tip-bot for Thomas Gleixner
2016-07-22 11:31 ` [patch 4 15/22] timer: Remove slack leftovers Jason A. Donenfeld
2016-07-22 13:04 ` Thomas Gleixner
2016-07-22 15:18 ` Jason A. Donenfeld
2016-07-22 22:54 ` Jason A. Donenfeld
2016-07-04 9:50 ` [patch 4 16/22] timer: Move __run_timers() function Thomas Gleixner
2016-07-07 8:46 ` [tip:timers/core] timers: " tip-bot for Anna-Maria Gleixner
2016-07-04 9:50 ` [patch 4 17/22] timer: Optimize collect timers for NOHZ Thomas Gleixner
2016-07-07 8:47 ` [tip:timers/core] timers: Optimize collect_expired_timers() " tip-bot for Anna-Maria Gleixner
2016-07-04 9:50 ` [patch 4 18/22] tick/sched: Remove pointless empty function Thomas Gleixner
2016-07-07 8:47 ` [tip:timers/core] timers/nohz: Remove pointless tick_nohz_kick_tick() function tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 19/22] timer: Forward wheel clock whenever possible Thomas Gleixner
2016-07-07 8:48 ` [tip:timers/core] timers: Forward the " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 20/22] timer: Only wake softirq if necessary Thomas Gleixner
2016-07-07 8:48 ` [tip:timers/core] timers: " tip-bot for Thomas Gleixner
2016-07-04 9:50 ` [patch 4 21/22] timer: Split out index calculation Thomas Gleixner
2016-07-07 8:48 ` [tip:timers/core] timers: " tip-bot for Anna-Maria Gleixner
2016-07-04 9:50 ` [patch 4 22/22] timer: Optimization for same expiry time in mod_timer() Thomas Gleixner
2016-07-07 8:49 ` [tip:timers/core] timers: Implement optimization " tip-bot for Anna-Maria Gleixner
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