0ec656eb71
For the fastpath, we want to tick, but undo the tick and jump to the slowpath if ticker would fire.
92 lines
2.2 KiB
C
92 lines
2.2 KiB
C
#ifndef JEMALLOC_INTERNAL_TICKER_H
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#define JEMALLOC_INTERNAL_TICKER_H
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#include "jemalloc/internal/util.h"
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/**
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* A ticker makes it easy to count-down events until some limit. You
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* ticker_init the ticker to trigger every nticks events. You then notify it
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* that an event has occurred with calls to ticker_tick (or that nticks events
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* have occurred with a call to ticker_ticks), which will return true (and reset
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* the counter) if the countdown hit zero.
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*/
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typedef struct {
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int32_t tick;
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int32_t nticks;
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} ticker_t;
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static inline void
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ticker_init(ticker_t *ticker, int32_t nticks) {
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ticker->tick = nticks;
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ticker->nticks = nticks;
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}
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static inline void
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ticker_copy(ticker_t *ticker, const ticker_t *other) {
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*ticker = *other;
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}
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static inline int32_t
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ticker_read(const ticker_t *ticker) {
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return ticker->tick;
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}
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/*
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* Not intended to be a public API. Unfortunately, on x86, neither gcc nor
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* clang seems smart enough to turn
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* ticker->tick -= nticks;
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* if (unlikely(ticker->tick < 0)) {
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* fixup ticker
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* return true;
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* }
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* return false;
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* into
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* subq %nticks_reg, (%ticker_reg)
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* js fixup ticker
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*
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* unless we force "fixup ticker" out of line. In that case, gcc gets it right,
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* but clang now does worse than before. So, on x86 with gcc, we force it out
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* of line, but otherwise let the inlining occur. Ordinarily this wouldn't be
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* worth the hassle, but this is on the fast path of both malloc and free (via
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* tcache_event).
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*/
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#if defined(__GNUC__) && !defined(__clang__) \
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&& (defined(__x86_64__) || defined(__i386__))
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JEMALLOC_NOINLINE
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#endif
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static bool
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ticker_fixup(ticker_t *ticker) {
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ticker->tick = ticker->nticks;
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return true;
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}
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static inline bool
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ticker_ticks(ticker_t *ticker, int32_t nticks) {
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ticker->tick -= nticks;
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if (unlikely(ticker->tick < 0)) {
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return ticker_fixup(ticker);
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}
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return false;
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}
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static inline bool
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ticker_tick(ticker_t *ticker) {
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return ticker_ticks(ticker, 1);
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}
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/*
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* Try to tick. If ticker would fire, return true, but rely on
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* slowpath to reset ticker.
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*/
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static inline bool
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ticker_trytick(ticker_t *ticker) {
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--ticker->tick;
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if (unlikely(ticker->tick < 0)) {
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return true;
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}
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return false;
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}
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#endif /* JEMALLOC_INTERNAL_TICKER_H */
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