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From: Stanislaw Gruszka <sgruszka@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Ingo Molnar" <mingo@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] sched: Lower chances of cputime scaling overflow
Date: Sat, 13 Apr 2013 16:55:38 +0200	[thread overview]
Message-ID: <20130413145538.GB11556@redhat.com> (raw)
In-Reply-To: <CA+55aFway4C89fTewKvED4RvFLaNdM-BVtkJ2YChsvracLKiyA@mail.gmail.com>

On Thu, Apr 11, 2013 at 08:38:37AM -0700, Linus Torvalds wrote:
>     /* We know one of the values has a bit set in the high 32 bits */
>     for (;;) {
>         /* Make sure "stime" is the bigger of stime/rtime */
>         if (rtime > stime) {
>             u64 tmp = stime; stime = rtime; rtime = tmp;
>         }

For most workloads rtime is bigger than stime, so swapping those would
save some cycles on common cases. Otherwise this algorithm looks great.

Thanks
Stanislaw


      parent reply	other threads:[~2013-04-13 14:54 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <tip-d9a3c9823a2e6a543eb7807fb3d15d8233817ec5@git.kernel.org>
2013-03-26 14:01 ` [tip:sched/core] sched: Lower chances of cputime scaling overflow Stanislaw Gruszka
2013-03-26 14:19   ` Frederic Weisbecker
2013-03-26 16:54     ` Stanislaw Gruszka
2013-04-10 12:51     ` Ingo Molnar
2013-04-10 15:28       ` Frederic Weisbecker
2013-04-10 17:32         ` Ingo Molnar
2013-04-11  8:04           ` Stanislaw Gruszka
2013-04-11 13:45   ` Peter Zijlstra
2013-04-11 14:50     ` Stanislaw Gruszka
2013-04-11 17:31       ` Peter Zijlstra
2013-04-11 15:38     ` Linus Torvalds
2013-04-11 18:07       ` Peter Zijlstra
2013-04-11 18:22         ` Frederic Weisbecker
2013-04-11 18:26           ` Frederic Weisbecker
2013-04-11 18:22         ` Linus Torvalds
2013-04-12  7:55       ` Peter Zijlstra
2013-04-13 14:49         ` Stanislaw Gruszka
2013-04-13 18:44           ` Linus Torvalds
2013-04-16 10:40             ` Stanislaw Gruszka
2013-04-30 14:03             ` Stanislaw Gruszka
2013-04-13 14:55       ` Stanislaw Gruszka [this message]

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