timers, sched/clock: Clean up the code a bit
Trivial cleanups, to improve the readability of the generic sched_clock() code:
- Improve and standardize comments
- Standardize the coding style
- Use vertical spacing where appropriate
- etc.
No code changed:
md5:
19a053b31e0c54feaeff1492012b019a sched_clock.o.before.asm
19a053b31e0c54feaeff1492012b019a sched_clock.o.after.asm
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
Родитель
1809bfa44e
Коммит
32fea568ae
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@ -1,5 +1,6 @@
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/*
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* sched_clock.c: support for extending counters to full 64-bit ns counter
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* sched_clock.c: Generic sched_clock() support, to extend low level
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* hardware time counters to full 64-bit ns values.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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@ -19,15 +20,15 @@
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#include <linux/bitops.h>
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/**
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* struct clock_read_data - data required to read from sched_clock
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* struct clock_read_data - data required to read from sched_clock()
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*
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* @epoch_ns: sched_clock value at last update
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* @epoch_cyc: Clock cycle value at last update
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* @epoch_ns: sched_clock() value at last update
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* @epoch_cyc: Clock cycle value at last update.
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* @sched_clock_mask: Bitmask for two's complement subtraction of non 64bit
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* clocks
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* @read_sched_clock: Current clock source (or dummy source when suspended)
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* @mult: Multipler for scaled math conversion
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* @shift: Shift value for scaled math conversion
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* clocks.
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* @read_sched_clock: Current clock source (or dummy source when suspended).
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* @mult: Multipler for scaled math conversion.
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* @shift: Shift value for scaled math conversion.
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*
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* Care must be taken when updating this structure; it is read by
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* some very hot code paths. It occupies <=40 bytes and, when combined
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@ -44,25 +45,26 @@ struct clock_read_data {
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};
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/**
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* struct clock_data - all data needed for sched_clock (including
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* struct clock_data - all data needed for sched_clock() (including
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* registration of a new clock source)
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*
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* @seq: Sequence counter for protecting updates. The lowest
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* bit is the index for @read_data.
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* @read_data: Data required to read from sched_clock.
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* @wrap_kt: Duration for which clock can run before wrapping
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* @rate: Tick rate of the registered clock
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* @actual_read_sched_clock: Registered clock read function
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* @wrap_kt: Duration for which clock can run before wrapping.
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* @rate: Tick rate of the registered clock.
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* @actual_read_sched_clock: Registered hardware level clock read function.
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*
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* The ordering of this structure has been chosen to optimize cache
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* performance. In particular seq and read_data[0] (combined) should fit
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* into a single 64 byte cache line.
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* performance. In particular 'seq' and 'read_data[0]' (combined) should fit
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* into a single 64-byte cache line.
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*/
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struct clock_data {
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seqcount_t seq;
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struct clock_read_data read_data[2];
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ktime_t wrap_kt;
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unsigned long rate;
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u64 (*actual_read_sched_clock)(void);
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};
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@ -112,10 +114,10 @@ unsigned long long notrace sched_clock(void)
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/*
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* Updating the data required to read the clock.
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*
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* sched_clock will never observe mis-matched data even if called from
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* sched_clock() will never observe mis-matched data even if called from
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* an NMI. We do this by maintaining an odd/even copy of the data and
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* steering sched_clock to one or the other using a sequence counter.
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* In order to preserve the data cache profile of sched_clock as much
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* steering sched_clock() to one or the other using a sequence counter.
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* In order to preserve the data cache profile of sched_clock() as much
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* as possible the system reverts back to the even copy when the update
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* completes; the odd copy is used *only* during an update.
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*/
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@ -135,7 +137,7 @@ static void update_clock_read_data(struct clock_read_data *rd)
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}
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/*
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* Atomically update the sched_clock epoch.
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* Atomically update the sched_clock() epoch.
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*/
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static void update_sched_clock(void)
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{
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@ -146,9 +148,7 @@ static void update_sched_clock(void)
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rd = cd.read_data[0];
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cyc = cd.actual_read_sched_clock();
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ns = rd.epoch_ns +
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cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask,
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rd.mult, rd.shift);
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ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
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rd.epoch_ns = ns;
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rd.epoch_cyc = cyc;
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@ -160,11 +160,12 @@ static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
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{
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update_sched_clock();
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hrtimer_forward_now(hrt, cd.wrap_kt);
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return HRTIMER_RESTART;
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}
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void __init sched_clock_register(u64 (*read)(void), int bits,
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unsigned long rate)
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void __init
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sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
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{
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u64 res, wrap, new_mask, new_epoch, cyc, ns;
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u32 new_mult, new_shift;
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@ -177,24 +178,22 @@ void __init sched_clock_register(u64 (*read)(void), int bits,
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WARN_ON(!irqs_disabled());
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/* calculate the mult/shift to convert counter ticks to ns. */
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/* Calculate the mult/shift to convert counter ticks to ns. */
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clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
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new_mask = CLOCKSOURCE_MASK(bits);
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cd.rate = rate;
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/* calculate how many nanosecs until we risk wrapping */
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/* Calculate how many nanosecs until we risk wrapping */
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wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL);
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cd.wrap_kt = ns_to_ktime(wrap);
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rd = cd.read_data[0];
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/* update epoch for new counter and update epoch_ns from old counter*/
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/* Update epoch for new counter and update 'epoch_ns' from old counter*/
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new_epoch = read();
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cyc = cd.actual_read_sched_clock();
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ns = rd.epoch_ns +
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cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask,
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rd.mult, rd.shift);
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ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
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cd.actual_read_sched_clock = read;
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rd.read_sched_clock = read;
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@ -203,25 +202,29 @@ void __init sched_clock_register(u64 (*read)(void), int bits,
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rd.shift = new_shift;
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rd.epoch_cyc = new_epoch;
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rd.epoch_ns = ns;
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update_clock_read_data(&rd);
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r = rate;
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if (r >= 4000000) {
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r /= 1000000;
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r_unit = 'M';
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} else if (r >= 1000) {
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} else {
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if (r >= 1000) {
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r /= 1000;
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r_unit = 'k';
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} else
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} else {
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r_unit = ' ';
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}
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}
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/* calculate the ns resolution of this counter */
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/* Calculate the ns resolution of this counter */
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res = cyc_to_ns(1ULL, new_mult, new_shift);
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pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",
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bits, r, r_unit, res, wrap);
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/* Enable IRQ time accounting if we have a fast enough sched_clock */
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/* Enable IRQ time accounting if we have a fast enough sched_clock() */
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if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
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enable_sched_clock_irqtime();
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@ -231,7 +234,7 @@ void __init sched_clock_register(u64 (*read)(void), int bits,
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void __init sched_clock_postinit(void)
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{
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/*
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* If no sched_clock function has been provided at that point,
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* If no sched_clock() function has been provided at that point,
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* make it the final one one.
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*/
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if (cd.actual_read_sched_clock == jiffy_sched_clock_read)
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@ -257,7 +260,7 @@ void __init sched_clock_postinit(void)
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* This function must only be called from the critical
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* section in sched_clock(). It relies on the read_seqcount_retry()
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* at the end of the critical section to be sure we observe the
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* correct copy of epoch_cyc.
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* correct copy of 'epoch_cyc'.
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*/
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static u64 notrace suspended_sched_clock_read(void)
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{
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@ -273,6 +276,7 @@ static int sched_clock_suspend(void)
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update_sched_clock();
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hrtimer_cancel(&sched_clock_timer);
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rd->read_sched_clock = suspended_sched_clock_read;
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return 0;
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}
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@ -293,6 +297,7 @@ static struct syscore_ops sched_clock_ops = {
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static int __init sched_clock_syscore_init(void)
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{
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register_syscore_ops(&sched_clock_ops);
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return 0;
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}
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device_initcall(sched_clock_syscore_init);
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