From: "George Spelvin" <linux@sciencehorizons.net>
To: linux@sciencehorizons.net, tglx@linutronix.de
Cc: edumazet@google.com, linux-kernel@vger.kernel.org,
peterz@infradead.org, richardcochran@gmail.com
Subject: Re: [patch 13/20] timer: Switch to a non cascading wheel
Date: 14 Jun 2016 06:15:06 -0400 [thread overview]
Message-ID: <20160614101506.30068.qmail@ns.sciencehorizons.net> (raw)
In-Reply-To: <alpine.DEB.2.11.1606141045191.5839@nanos>
On Tue, 14 Jun 2016, Thomas Gleixner wrote:
> I thought about that and when looking at those long timeout thingies
> I came to the conclusion that it's simply not worth the trouble.
Okay. A comment might be nice, just to stop someone else wasting
brain power on it. E.g.
/*
* If the timer happens to expire exactly now, this will cascade it to
* vectors[0] which we just cleared and won't check again for 64 jiffies.
* This is acceptable error on a timeout this long.
*/
>> to be replaced with __builtin_clz or similar:
>
> Except that __fls() is noticeably slower than the if chain.
Fair enogh. I wasn't sure about the distribution; if it's biased low,
then the if chain would win.
> That's not new code. We kept the ordering, but yes, we definitely can turn
> that around. The only restriction is that we get it before releasing the lock.
Thanks!
next prev parent reply other threads:[~2016-06-14 10:15 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-14 8:16 [patch 13/20] timer: Switch to a non cascading wheel George Spelvin
2016-06-14 8:50 ` Thomas Gleixner
2016-06-14 10:15 ` George Spelvin [this message]
2016-06-14 10:20 ` Peter Zijlstra
2016-06-14 12:58 ` George Spelvin
2016-06-14 16:48 ` Thomas Gleixner
2016-06-14 19:56 ` George Spelvin
-- strict thread matches above, loose matches on Subject: below --
2016-06-13 8:40 [patch 00/20] timer: Refactor the timer wheel Thomas Gleixner
2016-06-13 8:41 ` [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner
2016-06-13 11:40 ` Peter Zijlstra
2016-06-13 12:30 ` Thomas Gleixner
2016-06-13 12:46 ` Eric Dumazet
2016-06-13 14:30 ` Thomas Gleixner
2016-06-14 10:11 ` Ingo Molnar
2016-06-14 16:28 ` Thomas Gleixner
2016-06-14 17:14 ` Arjan van de Ven
2016-06-14 18:05 ` Thomas Gleixner
2016-06-14 20:34 ` Peter Zijlstra
2016-06-14 20:42 ` Peter Zijlstra
2016-06-14 21:17 ` Eric Dumazet
2016-06-15 14:53 ` Thomas Gleixner
2016-06-15 14:55 ` Arjan van de Ven
2016-06-15 16:43 ` Thomas Gleixner
2016-06-16 15:43 ` Thomas Gleixner
2016-06-16 16:02 ` Paul E. McKenney
2016-06-16 18:14 ` Peter Zijlstra
2016-06-17 0:40 ` Paul E. McKenney
2016-06-17 4:04 ` Paul E. McKenney
2016-06-16 16:04 ` Arjan van de Ven
2016-06-16 16:09 ` Thomas Gleixner
2016-06-15 15:05 ` Eric Dumazet
2016-06-13 14:36 ` Richard Cochran
2016-06-13 14:39 ` Thomas Gleixner
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