[NET_SCHED]: Use ktime as clocksource
Get rid of the manual clock source selection mess and use ktime. Also use a scalar representation, which allows to clean up pkt_sched.h a bit more and results in less ktime_to_ns() calls in most cases. The PSCHED_US2JIFFIE/PSCHED_JIFFIE2US macros are implemented quite inefficient by this patch, following patches will convert all qdiscs to hrtimers and get rid of them entirely. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy
David S. Miller
Родитель
ddc7b8e32b
Коммит
641b9e0e8b
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@ -2,6 +2,7 @@
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#define __NET_PKT_SCHED_H
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#include <linux/jiffies.h>
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#include <linux/ktime.h>
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#include <net/sch_generic.h>
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struct qdisc_walker
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@ -37,176 +38,32 @@ static inline void *qdisc_priv(struct Qdisc *q)
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The things are not so bad, because we may use artifical
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clock evaluated by integration of network data flow
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in the most critical places.
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Note: we do not use fastgettimeofday.
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The reason is that, when it is not the same thing as
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gettimeofday, it returns invalid timestamp, which is
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not updated, when net_bh is active.
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*/
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/* General note about internal clock.
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Any clock source returns time intervals, measured in units
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close to 1usec. With source CONFIG_NET_SCH_CLK_GETTIMEOFDAY it is precisely
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microseconds, otherwise something close but different chosen to minimize
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arithmetic cost. Ratio usec/internal untis in form nominator/denominator
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may be read from /proc/net/psched.
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*/
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#ifdef CONFIG_NET_SCH_CLK_GETTIMEOFDAY
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typedef struct timeval psched_time_t;
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typedef long psched_tdiff_t;
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#define PSCHED_GET_TIME(stamp) do_gettimeofday(&(stamp))
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#define PSCHED_US2JIFFIE(usecs) usecs_to_jiffies(usecs)
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#define PSCHED_JIFFIE2US(delay) jiffies_to_usecs(delay)
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#else /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
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typedef u64 psched_time_t;
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typedef long psched_tdiff_t;
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#ifdef CONFIG_NET_SCH_CLK_JIFFIES
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/* Avoid doing 64 bit divide by 1000 */
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#define PSCHED_US2NS(x) ((s64)(x) << 10)
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#define PSCHED_NS2US(x) ((x) >> 10)
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#if HZ < 96
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#define PSCHED_JSCALE 14
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#elif HZ >= 96 && HZ < 192
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#define PSCHED_JSCALE 13
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#elif HZ >= 192 && HZ < 384
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#define PSCHED_JSCALE 12
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#elif HZ >= 384 && HZ < 768
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#define PSCHED_JSCALE 11
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#elif HZ >= 768
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#define PSCHED_JSCALE 10
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#endif
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#define PSCHED_TICKS_PER_SEC PSCHED_NS2US(NSEC_PER_SEC)
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#define PSCHED_GET_TIME(stamp) \
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((stamp) = PSCHED_NS2US(ktime_to_ns(ktime_get())))
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#define PSCHED_GET_TIME(stamp) ((stamp) = (get_jiffies_64()<<PSCHED_JSCALE))
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#define PSCHED_US2JIFFIE(delay) (((delay)+(1<<PSCHED_JSCALE)-1)>>PSCHED_JSCALE)
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#define PSCHED_JIFFIE2US(delay) ((delay)<<PSCHED_JSCALE)
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#endif /* CONFIG_NET_SCH_CLK_JIFFIES */
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#ifdef CONFIG_NET_SCH_CLK_CPU
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#include <asm/timex.h>
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extern psched_tdiff_t psched_clock_per_hz;
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extern int psched_clock_scale;
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extern psched_time_t psched_time_base;
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extern cycles_t psched_time_mark;
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#define PSCHED_GET_TIME(stamp) \
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do { \
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cycles_t cur = get_cycles(); \
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if (sizeof(cycles_t) == sizeof(u32)) { \
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if (cur <= psched_time_mark) \
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psched_time_base += 0x100000000ULL; \
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psched_time_mark = cur; \
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(stamp) = (psched_time_base + cur)>>psched_clock_scale; \
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} else { \
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(stamp) = cur>>psched_clock_scale; \
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} \
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} while (0)
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#define PSCHED_US2JIFFIE(delay) (((delay)+psched_clock_per_hz-1)/psched_clock_per_hz)
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#define PSCHED_JIFFIE2US(delay) ((delay)*psched_clock_per_hz)
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#endif /* CONFIG_NET_SCH_CLK_CPU */
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#endif /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
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#ifdef CONFIG_NET_SCH_CLK_GETTIMEOFDAY
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#define PSCHED_TDIFF(tv1, tv2) \
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({ \
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int __delta_sec = (tv1).tv_sec - (tv2).tv_sec; \
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int __delta = (tv1).tv_usec - (tv2).tv_usec; \
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if (__delta_sec) { \
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switch (__delta_sec) { \
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default: \
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__delta = 0; \
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case 2: \
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__delta += USEC_PER_SEC; \
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case 1: \
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__delta += USEC_PER_SEC; \
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} \
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} \
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__delta; \
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})
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static inline int
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psched_tod_diff(int delta_sec, int bound)
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{
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int delta;
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if (bound <= USEC_PER_SEC || delta_sec > (0x7FFFFFFF/USEC_PER_SEC)-1)
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return bound;
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delta = delta_sec * USEC_PER_SEC;
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if (delta > bound || delta < 0)
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delta = bound;
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return delta;
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}
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#define PSCHED_US2JIFFIE(usecs) usecs_to_jiffies(PSCHED_US2NS((usecs)) / NSEC_PER_USEC)
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#define PSCHED_JIFFIE2US(delay) PSCHED_NS2US(jiffies_to_usecs((delay)) * NSEC_PER_USEC)
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#define PSCHED_TDIFF(tv1, tv2) (long)((tv1) - (tv2))
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#define PSCHED_TDIFF_SAFE(tv1, tv2, bound) \
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({ \
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int __delta_sec = (tv1).tv_sec - (tv2).tv_sec; \
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int __delta = (tv1).tv_usec - (tv2).tv_usec; \
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switch (__delta_sec) { \
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default: \
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__delta = psched_tod_diff(__delta_sec, bound); break; \
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case 2: \
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__delta += USEC_PER_SEC; \
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case 1: \
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__delta += USEC_PER_SEC; \
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case 0: \
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if (__delta > bound || __delta < 0) \
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__delta = bound; \
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} \
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__delta; \
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})
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#define PSCHED_TLESS(tv1, tv2) (((tv1).tv_usec < (tv2).tv_usec && \
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(tv1).tv_sec <= (tv2).tv_sec) || \
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(tv1).tv_sec < (tv2).tv_sec)
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#define PSCHED_TADD2(tv, delta, tv_res) \
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({ \
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int __delta = (tv).tv_usec + (delta); \
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(tv_res).tv_sec = (tv).tv_sec; \
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while (__delta >= USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
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(tv_res).tv_usec = __delta; \
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})
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#define PSCHED_TADD(tv, delta) \
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({ \
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(tv).tv_usec += (delta); \
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while ((tv).tv_usec >= USEC_PER_SEC) { (tv).tv_sec++; \
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(tv).tv_usec -= USEC_PER_SEC; } \
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})
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/* Set/check that time is in the "past perfect";
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it depends on concrete representation of system time
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*/
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#define PSCHED_SET_PASTPERFECT(t) ((t).tv_sec = 0)
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#define PSCHED_IS_PASTPERFECT(t) ((t).tv_sec == 0)
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#define PSCHED_AUDIT_TDIFF(t) ({ if ((t) > 2000000) (t) = 2000000; })
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#else /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
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#define PSCHED_TDIFF(tv1, tv2) (long)((tv1) - (tv2))
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#define PSCHED_TDIFF_SAFE(tv1, tv2, bound) \
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min_t(long long, (tv1) - (tv2), bound)
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#define PSCHED_TLESS(tv1, tv2) ((tv1) < (tv2))
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min_t(long long, (tv1) - (tv2), bound)
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#define PSCHED_TLESS(tv1, tv2) ((tv1) < (tv2))
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#define PSCHED_TADD2(tv, delta, tv_res) ((tv_res) = (tv) + (delta))
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#define PSCHED_TADD(tv, delta) ((tv) += (delta))
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#define PSCHED_TADD(tv, delta) ((tv) += (delta))
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#define PSCHED_SET_PASTPERFECT(t) ((t) = 0)
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#define PSCHED_IS_PASTPERFECT(t) ((t) == 0)
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#define PSCHED_AUDIT_TDIFF(t)
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#endif /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
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extern struct Qdisc_ops pfifo_qdisc_ops;
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extern struct Qdisc_ops bfifo_qdisc_ops;
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@ -59,6 +59,7 @@ ktime_t ktime_get(void)
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return timespec_to_ktime(now);
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}
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EXPORT_SYMBOL_GPL(ktime_get);
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/**
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* ktime_get_real - get the real (wall-) time in ktime_t format
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@ -46,62 +46,6 @@ config NET_SCH_FIFO
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if NET_SCHED
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choice
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prompt "Packet scheduler clock source"
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default NET_SCH_CLK_GETTIMEOFDAY
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---help---
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Packet schedulers need a monotonic clock that increments at a static
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rate. The kernel provides several suitable interfaces, each with
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different properties:
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- high resolution (us or better)
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- fast to read (minimal locking, no i/o access)
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- synchronized on all processors
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- handles cpu clock frequency changes
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but nothing provides all of the above.
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config NET_SCH_CLK_JIFFIES
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bool "Timer interrupt"
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---help---
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Say Y here if you want to use the timer interrupt (jiffies) as clock
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source. This clock source is fast, synchronized on all processors and
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handles cpu clock frequency changes, but its resolution is too low
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for accurate shaping except at very low speed.
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config NET_SCH_CLK_GETTIMEOFDAY
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bool "gettimeofday"
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---help---
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Say Y here if you want to use gettimeofday as clock source. This clock
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source has high resolution, is synchronized on all processors and
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handles cpu clock frequency changes, but it is slow.
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Choose this if you need a high resolution clock source but can't use
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the CPU's cycle counter.
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# don't allow on SMP x86 because they can have unsynchronized TSCs.
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# gettimeofday is a good alternative
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config NET_SCH_CLK_CPU
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bool "CPU cycle counter"
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depends on ((X86_TSC || X86_64) && !SMP) || ALPHA || SPARC64 || PPC64 || IA64
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---help---
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Say Y here if you want to use the CPU's cycle counter as clock source.
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This is a cheap and high resolution clock source, but on some
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architectures it is not synchronized on all processors and doesn't
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handle cpu clock frequency changes.
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The useable cycle counters are:
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x86/x86_64 - Timestamp Counter
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alpha - Cycle Counter
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sparc64 - %ticks register
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ppc64 - Time base
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ia64 - Interval Time Counter
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Choose this if your CPU's cycle counter is working properly.
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endchoice
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comment "Queueing/Scheduling"
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config NET_SCH_CBQ
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@ -1175,15 +1175,12 @@ reclassify:
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return -1;
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}
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static int psched_us_per_tick = 1;
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static int psched_tick_per_us = 1;
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#ifdef CONFIG_PROC_FS
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static int psched_show(struct seq_file *seq, void *v)
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{
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seq_printf(seq, "%08x %08x %08x %08x\n",
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psched_tick_per_us, psched_us_per_tick,
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1000000, HZ);
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(u32)NSEC_PER_USEC, (u32)PSCHED_US2NS(1),
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1000000, HZ);
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return 0;
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}
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@ -1202,80 +1199,10 @@ static const struct file_operations psched_fops = {
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};
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#endif
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#ifdef CONFIG_NET_SCH_CLK_CPU
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psched_tdiff_t psched_clock_per_hz;
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int psched_clock_scale;
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EXPORT_SYMBOL(psched_clock_per_hz);
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EXPORT_SYMBOL(psched_clock_scale);
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psched_time_t psched_time_base;
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cycles_t psched_time_mark;
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EXPORT_SYMBOL(psched_time_mark);
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EXPORT_SYMBOL(psched_time_base);
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/*
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* Periodically adjust psched_time_base to avoid overflow
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* with 32-bit get_cycles(). Safe up to 4GHz CPU.
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*/
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static void psched_tick(unsigned long);
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static DEFINE_TIMER(psched_timer, psched_tick, 0, 0);
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static void psched_tick(unsigned long dummy)
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{
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if (sizeof(cycles_t) == sizeof(u32)) {
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psched_time_t dummy_stamp;
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PSCHED_GET_TIME(dummy_stamp);
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psched_timer.expires = jiffies + 1*HZ;
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add_timer(&psched_timer);
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}
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}
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int __init psched_calibrate_clock(void)
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{
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psched_time_t stamp, stamp1;
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struct timeval tv, tv1;
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psched_tdiff_t delay;
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long rdelay;
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unsigned long stop;
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psched_tick(0);
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stop = jiffies + HZ/10;
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PSCHED_GET_TIME(stamp);
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do_gettimeofday(&tv);
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while (time_before(jiffies, stop)) {
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barrier();
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cpu_relax();
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}
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PSCHED_GET_TIME(stamp1);
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do_gettimeofday(&tv1);
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delay = PSCHED_TDIFF(stamp1, stamp);
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rdelay = tv1.tv_usec - tv.tv_usec;
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rdelay += (tv1.tv_sec - tv.tv_sec)*1000000;
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if (rdelay > delay)
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return -1;
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delay /= rdelay;
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psched_tick_per_us = delay;
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while ((delay>>=1) != 0)
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psched_clock_scale++;
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psched_us_per_tick = 1<<psched_clock_scale;
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psched_clock_per_hz = (psched_tick_per_us*(1000000/HZ))>>psched_clock_scale;
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return 0;
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}
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#endif
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static int __init pktsched_init(void)
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{
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struct rtnetlink_link *link_p;
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#ifdef CONFIG_NET_SCH_CLK_CPU
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if (psched_calibrate_clock() < 0)
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return -1;
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#elif defined(CONFIG_NET_SCH_CLK_JIFFIES)
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psched_tick_per_us = HZ<<PSCHED_JSCALE;
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psched_us_per_tick = 1000000;
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#endif
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link_p = rtnetlink_links[PF_UNSPEC];
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/* Setup rtnetlink links. It is made here to avoid
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@ -195,20 +195,6 @@ struct hfsc_sched
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struct timer_list wd_timer; /* watchdog timer */
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};
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/*
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* macros
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*/
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#ifdef CONFIG_NET_SCH_CLK_GETTIMEOFDAY
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#include <linux/time.h>
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#undef PSCHED_GET_TIME
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#define PSCHED_GET_TIME(stamp) \
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do { \
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struct timeval tv; \
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do_gettimeofday(&tv); \
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(stamp) = 1ULL * USEC_PER_SEC * tv.tv_sec + tv.tv_usec; \
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} while (0)
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#endif
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#define HT_INFINITY 0xffffffffffffffffULL /* infinite time value */
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@ -394,28 +380,17 @@ cftree_update(struct hfsc_class *cl)
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* ism: (psched_us/byte) << ISM_SHIFT
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* dx: psched_us
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*
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* Clock source resolution (CONFIG_NET_SCH_CLK_*)
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* JIFFIES: for 48<=HZ<=1534 resolution is between 0.63us and 1.27us.
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* CPU: resolution is between 0.5us and 1us.
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* GETTIMEOFDAY: resolution is exactly 1us.
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* The clock source resolution with ktime is 1.024us.
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*
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* sm and ism are scaled in order to keep effective digits.
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* SM_SHIFT and ISM_SHIFT are selected to keep at least 4 effective
|
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* digits in decimal using the following table.
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*
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* Note: We can afford the additional accuracy (altq hfsc keeps at most
|
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* 3 effective digits) thanks to the fact that linux clock is bounded
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* much more tightly.
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*
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* bits/sec 100Kbps 1Mbps 10Mbps 100Mbps 1Gbps
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* ------------+-------------------------------------------------------
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* bytes/0.5us 6.25e-3 62.5e-3 625e-3 6250e-e 62500e-3
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* bytes/us 12.5e-3 125e-3 1250e-3 12500e-3 125000e-3
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* bytes/1.27us 15.875e-3 158.75e-3 1587.5e-3 15875e-3 158750e-3
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* bytes/1.024us 12.8e-3 128e-3 1280e-3 12800e-3 128000e-3
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*
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* 0.5us/byte 160 16 1.6 0.16 0.016
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* us/byte 80 8 0.8 0.08 0.008
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* 1.27us/byte 63 6.3 0.63 0.063 0.0063
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* 1.024us/byte 78.125 7.8125 0.78125 0.078125 0.0078125
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*/
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#define SM_SHIFT 20
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#define ISM_SHIFT 18
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