From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC PATCH] posix-cpu-timers: optimize calling thread_group_cputime()
Date: Fri, 12 Jun 2009 13:09:46 +0200 [thread overview]
Message-ID: <1244804986.6691.1224.camel@laptop> (raw)
In-Reply-To: <20090612123903.37cfd868@dhcp-lab-109.englab.brq.redhat.com>
On Fri, 2009-06-12 at 12:39 +0200, Stanislaw Gruszka wrote:
> - times->utime = cputime_add(times->utime, t->utime);
> - times->stime = cputime_add(times->stime, t->stime);
> - times->sum_exec_runtime += t->se.sum_exec_runtime;
> + if (mask & TG_CPUCLOCK_UTIME)
> + times->utime = cputime_add(times->utime, t->utime);
> + if (mask & TG_CPUCLOCK_STIME)
> + times->stime = cputime_add(times->stime, t->stime);
> + if (mask & TG_CPUCLOCK_SCHED)
> + times->sum_exec_runtime += t->se.sum_exec_runtime;
Does adding 3 branches really make it faster? Since you're bound to want
at least one, I would expect the cacheline to be hot (assuming all three
variables live in the same cacheline -- if not, they should be!), so all
you're avoiding is the addition.
next prev parent reply other threads:[~2009-06-12 11:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-12 10:39 [RFC PATCH] posix-cpu-timers: optimize calling thread_group_cputime() Stanislaw Gruszka
2009-06-12 11:09 ` Peter Zijlstra [this message]
2009-06-12 11:20 ` Stanislaw Gruszka
2009-06-12 14:25 ` Oleg Nesterov
2009-06-15 8:55 ` Stanislaw Gruszka
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