1 #ifndef JEMALLOC_INTERNAL_TICKER_H
2 #define JEMALLOC_INTERNAL_TICKER_H
3
4 #include "jemalloc/internal/util.h"
5
6 /**
7 * A ticker makes it easy to count-down events until some limit. You
8 * ticker_init the ticker to trigger every nticks events. You then notify it
9 * that an event has occurred with calls to ticker_tick (or that nticks events
10 * have occurred with a call to ticker_ticks), which will return true (and reset
11 * the counter) if the countdown hit zero.
12 */
13
14 typedef struct {
15 int32_t tick;
16 int32_t nticks;
17 } ticker_t;
18
19 static inline void
ticker_init(ticker_t * ticker,int32_t nticks)20 ticker_init(ticker_t *ticker, int32_t nticks) {
21 ticker->tick = nticks;
22 ticker->nticks = nticks;
23 }
24
25 static inline void
ticker_copy(ticker_t * ticker,const ticker_t * other)26 ticker_copy(ticker_t *ticker, const ticker_t *other) {
27 *ticker = *other;
28 }
29
30 static inline int32_t
ticker_read(const ticker_t * ticker)31 ticker_read(const ticker_t *ticker) {
32 return ticker->tick;
33 }
34
35 /*
36 * Not intended to be a public API. Unfortunately, on x86, neither gcc nor
37 * clang seems smart enough to turn
38 * ticker->tick -= nticks;
39 * if (unlikely(ticker->tick < 0)) {
40 * fixup ticker
41 * return true;
42 * }
43 * return false;
44 * into
45 * subq %nticks_reg, (%ticker_reg)
46 * js fixup ticker
47 *
48 * unless we force "fixup ticker" out of line. In that case, gcc gets it right,
49 * but clang now does worse than before. So, on x86 with gcc, we force it out
50 * of line, but otherwise let the inlining occur. Ordinarily this wouldn't be
51 * worth the hassle, but this is on the fast path of both malloc and free (via
52 * tcache_event).
53 */
54 #if defined(__GNUC__) && !defined(__clang__) \
55 && (defined(__x86_64__) || defined(__i386__))
56 JEMALLOC_NOINLINE
57 #endif
58 static bool
ticker_fixup(ticker_t * ticker)59 ticker_fixup(ticker_t *ticker) {
60 ticker->tick = ticker->nticks;
61 return true;
62 }
63
64 static inline bool
ticker_ticks(ticker_t * ticker,int32_t nticks)65 ticker_ticks(ticker_t *ticker, int32_t nticks) {
66 ticker->tick -= nticks;
67 if (unlikely(ticker->tick < 0)) {
68 return ticker_fixup(ticker);
69 }
70 return false;
71 }
72
73 static inline bool
ticker_tick(ticker_t * ticker)74 ticker_tick(ticker_t *ticker) {
75 return ticker_ticks(ticker, 1);
76 }
77
78 /*
79 * Try to tick. If ticker would fire, return true, but rely on
80 * slowpath to reset ticker.
81 */
82 static inline bool
ticker_trytick(ticker_t * ticker)83 ticker_trytick(ticker_t *ticker) {
84 --ticker->tick;
85 if (unlikely(ticker->tick < 0)) {
86 return true;
87 }
88 return false;
89 }
90
91 #endif /* JEMALLOC_INTERNAL_TICKER_H */
92