lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 24 Mar 2015 09:41:18 +0000 From: Morten Rasmussen <morten.rasmussen@....com> To: Peter Zijlstra <peterz@...radead.org> Cc: "mingo@...hat.com" <mingo@...hat.com>, "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>, Dietmar Eggemann <Dietmar.Eggemann@....com>, "yuyang.du@...el.com" <yuyang.du@...el.com>, "preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>, "mturquette@...aro.org" <mturquette@...aro.org>, "nico@...aro.org" <nico@...aro.org>, "rjw@...ysocki.net" <rjw@...ysocki.net>, Juri Lelli <Juri.Lelli@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Russell King <linux@....linux.org.uk> Subject: Re: [RFCv3 PATCH 14/48] arm: Frequency invariant scheduler load-tracking support On Mon, Mar 23, 2015 at 01:39:44PM +0000, Peter Zijlstra wrote: > On Wed, Feb 04, 2015 at 06:30:51PM +0000, Morten Rasmussen wrote: > > +/* cpufreq callback function setting current cpu frequency */ > > +void arch_scale_set_curr_freq(int cpu, unsigned long freq) > > +{ > > + atomic_long_set(&per_cpu(cpu_curr_freq, cpu), freq); > > +} > > + > > +/* cpufreq callback function setting max cpu frequency */ > > +void arch_scale_set_max_freq(int cpu, unsigned long freq) > > +{ > > + atomic_long_set(&per_cpu(cpu_max_freq, cpu), freq); > > +} > > + > > +unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu) > > +{ > > + unsigned long curr = atomic_long_read(&per_cpu(cpu_curr_freq, cpu)); > > + unsigned long max = atomic_long_read(&per_cpu(cpu_max_freq, cpu)); > > + > > + if (!curr || !max) > > + return SCHED_CAPACITY_SCALE; > > + > > + return (curr * SCHED_CAPACITY_SCALE) / max; > > +} > > so I've no idea how many cycles an (integer) division takes on ARM; but > doesn't it make sense to do this division (once) in > arch_scale_set_curr_freq() instead of every time we need the result? It does. In fact I have already prepared that fix for v4. Integer division is expensive ARM and we call this function a lot. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists