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Message-Id: <1180081329.7348.44.camel@twins>
Date: Fri, 25 May 2007 10:22:09 +0200
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: Ingo Molnar <mingo@...e.hu>
Cc: Andi Kleen <andi@...stfloor.org>,
Satyam Sharma <satyam.sharma@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [patch] sched_clock(): cleanups
On Fri, 2007-05-25 at 09:49 +0200, Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
>
> > updated version of the cleanup patch below, renamed r_s_c to
> > resync_freq, and changed 'f' to 'freq'.
>
> updated one below.
>
> Ingo
>
> ------------------->
> Subject: [patch] sched_clock(): cleanups
> From: Ingo Molnar <mingo@...e.hu>
>
> clean up sched-clock.c - mostly comment style fixes.
>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Looks good.
> ---
> arch/i386/kernel/sched-clock.c | 110 +++++++++++++++++++++++++----------------
> 1 file changed, 69 insertions(+), 41 deletions(-)
>
> Index: linux-cfs-2.6.22-rc2-mm1.q/arch/i386/kernel/sched-clock.c
> ===================================================================
> --- linux-cfs-2.6.22-rc2-mm1.q.orig/arch/i386/kernel/sched-clock.c
> +++ linux-cfs-2.6.22-rc2-mm1.q/arch/i386/kernel/sched-clock.c
> @@ -60,18 +60,20 @@ DEFINE_PER_CPU(struct sc_data, sc_data)
> */
> unsigned long long native_sched_clock(void)
> {
> - unsigned long long r;
> struct sc_data *sc = &get_cpu_var(sc_data);
> + unsigned long long r;
> + unsigned long flags;
>
> if (sc->unstable) {
> - unsigned long flags;
> r = (jiffies_64 - sc->sync_base) * (1000000000 / HZ);
> r += sc->ns_base;
> local_irq_save(flags);
> - /* last_val is used to avoid non monotonity on a
> - stable->unstable transition. Make sure the time
> - never goes to before the last value returned by
> - the TSC clock */
> + /*
> + * last_val is used to avoid non monotonity on a
> + * stable->unstable transition. Make sure the time
> + * never goes to before the last value returned by
> + * the TSC clock
> + */
> if (r <= sc->last_val)
> r = sc->last_val + 1;
> sc->last_val = r;
> @@ -87,8 +89,10 @@ unsigned long long native_sched_clock(vo
> return r;
> }
>
> -/* We need to define a real function for sched_clock, to override the
> - weak default version */
> +/*
> + * We need to define a real function for sched_clock, to override the
> + * weak default version
> + */
> #ifdef CONFIG_PARAVIRT
> unsigned long long sched_clock(void)
> {
> @@ -101,9 +105,11 @@ unsigned long long sched_clock(void)
>
> static int no_sc_for_printk;
>
> -/* printk clock: when it is known the sc results are very non monotonic
> - fall back to jiffies for printk. Other sched_clock users are supposed
> - to handle this. */
> +/*
> + * printk clock: when it is known the sc results are very non monotonic
> + * fall back to jiffies for printk. Other sched_clock users are supposed
> + * to handle this.
> + */
> unsigned long long printk_clock(void)
> {
> if (unlikely(no_sc_for_printk))
> @@ -119,35 +125,46 @@ static void resync_sc_freq(struct sc_dat
> sc->unstable = 1;
> return;
> }
> - /* Handle nesting, but when we're zero multiple calls in a row
> - are ok too and not a bug */
> + /*
> + * Handle nesting, but when we're zero multiple calls in a row
> + * are ok too and not a bug
> + */
> if (sc->unstable > 0)
> sc->unstable--;
> if (sc->unstable)
> return;
> - /* RED-PEN protect with seqlock? I hope that's not needed
> - because sched_clock callers should be able to tolerate small
> - errors. */
> + /*
> + * RED-PEN protect with seqlock? I hope that's not needed
> + * because sched_clock callers should be able to tolerate small
> + * errors.
> + */
> sc->ns_base = ktime_to_ns(ktime_get());
> rdtscll(sc->sync_base);
> sc->cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR) / newfreq;
> }
>
> -static void call_r_s_f(void *arg)
> +static void __resync_freq(void *arg)
> {
> - struct cpufreq_freqs *freq = arg;
> - unsigned f = freq->new;
> - if (!f)
> - f = cpufreq_get(freq->cpu);
> - if (!f)
> - f = tsc_khz;
> - resync_sc_freq(&per_cpu(sc_data, freq->cpu), f);
> + struct cpufreq_freqs *freqp = arg;
> + unsigned freq = freqp->new;
> +
> + if (!freq) {
> + freq = cpufreq_get(freqp->cpu);
> + /*
> + * Still no frequency? Then fall back to tsc_khz:
> + */
> + if (!freq)
> + freq = tsc_khz;
> + }
> + resync_sc_freq(&per_cpu(sc_data, freqp->cpu), freq);
> }
>
> -static void call_r_s_f_here(void *arg)
> +static void resync_freq(void *arg)
> {
> - struct cpufreq_freqs f = { .cpu = get_cpu(), .new = 0 };
> - call_r_s_f(&f);
> + struct cpufreq_freqs f = { .new = 0 };
> +
> + f.cpu = get_cpu();
> + __resync_freq(&f);
> put_cpu();
> }
>
> @@ -155,9 +172,11 @@ static int sc_freq_event(struct notifier
> void *data)
> {
> struct cpufreq_freqs *freq = data;
> - int cpu = get_cpu();
> - struct sc_data *sc = &per_cpu(sc_data, cpu);
> + struct sc_data *sc;
> + int cpu;
>
> + cpu = get_cpu();
> + sc = &per_cpu(sc_data, cpu);
> if (cpu_has(&cpu_data[cpu], X86_FEATURE_CONSTANT_TSC))
> goto out;
> if (freq->old == freq->new)
> @@ -167,25 +186,30 @@ static int sc_freq_event(struct notifier
> case CPUFREQ_SUSPENDCHANGE:
> /* Mark TSC unstable during suspend/resume */
> case CPUFREQ_PRECHANGE:
> - /* Mark TSC as unstable until cpu frequency change is done
> - because we don't know when exactly it will change.
> - unstable in used as a counter to guard against races
> - between the cpu frequency notifiers and normal resyncs */
> + /*
> + * Mark TSC as unstable until cpu frequency change is done
> + * because we don't know when exactly it will change.
> + * unstable in used as a counter to guard against races
> + * between the cpu frequency notifiers and normal resyncs
> + */
> sc->unstable++;
> /* FALL THROUGH */
> case CPUFREQ_RESUMECHANGE:
> case CPUFREQ_POSTCHANGE:
> - /* Frequency change or resume is done -- update everything and
> - mark TSC as stable again. */
> + /*
> + * Frequency change or resume is done -- update everything
> + * and mark TSC as stable again.
> + */
> if (cpu == freq->cpu)
> resync_sc_freq(sc, freq->new);
> else
> - smp_call_function_single(freq->cpu, call_r_s_f,
> + smp_call_function_single(freq->cpu, __resync_freq,
> freq, 0, 1);
> break;
> }
> out:
> put_cpu();
> +
> return NOTIFY_DONE;
> }
>
> @@ -197,9 +221,11 @@ static int __cpuinit
> sc_cpu_event(struct notifier_block *self, unsigned long event, void *hcpu)
> {
> long cpu = (long)hcpu;
> +
> if (event == CPU_ONLINE) {
> struct cpufreq_freqs f = { .cpu = cpu, .new = 0 };
> - smp_call_function_single(cpu, call_r_s_f, &f, 0, 1);
> +
> + smp_call_function_single(cpu, __resync_freq, &f, 0, 1);
> }
> return NOTIFY_DONE;
> }
> @@ -209,13 +235,15 @@ static __init int init_sched_clock(void)
> if (unsynchronized_tsc())
> no_sc_for_printk = 1;
>
> - /* On a race between the various events the initialization might be
> - done multiple times, but code is tolerant to this */
> + /*
> + * On a race between the various events the initialization might be
> + * done multiple times, but code is tolerant to this
> + */
> cpufreq_register_notifier(&sc_freq_notifier,
> CPUFREQ_TRANSITION_NOTIFIER);
> hotcpu_notifier(sc_cpu_event, 0);
> - on_each_cpu(call_r_s_f_here, NULL, 0, 0);
> + on_each_cpu(resync_freq, NULL, 0, 0);
> +
> return 0;
> }
> core_initcall(init_sched_clock);
> -
-
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