diff options
| author | Warner Losh <imp@FreeBSD.org> | 2025-02-05 23:20:13 +0000 |
|---|---|---|
| committer | Warner Losh <imp@FreeBSD.org> | 2025-02-05 23:20:13 +0000 |
| commit | 48ec896efb0b78141df004eaa21288b84590c9da (patch) | |
| tree | 33799792fd95c266d472ab1ae51d50ab4f942eb3 /include/jemalloc/internal/ticker.h | |
| parent | d28d7fbede216494aa3942af042cc084fcd6098a (diff) | |
jemalloc: Import 5.3.0 54eaed1d8b56b1aa528be3bdd1877e59c56fa90cvendor/jemalloc/5.3.0vendor/jemalloc
Import jemalloc 5.3.0.
This import changes how manage the jemalloc vendor branch (which was
just started anyway). Starting with 5.3.0, we import a clean tree from
the upstream github, removing all the old files that are no longer
upstream, or that we've kept around for some reason. We do this because
we merge from this raw version of jemalloc into the FreeBSD
contrib/jemalloc, then we run autogen stuff, generate all the generated
.h files with gmake, then finally remove much of the generated files in
contrib/jemalloc using an update script.
Sponsored by: Netflix
Diffstat (limited to 'include/jemalloc/internal/ticker.h')
| -rw-r--r-- | include/jemalloc/internal/ticker.h | 92 |
1 files changed, 88 insertions, 4 deletions
diff --git a/include/jemalloc/internal/ticker.h b/include/jemalloc/internal/ticker.h index 52d0db4c89c6..6b51ddec43bf 100644 --- a/include/jemalloc/internal/ticker.h +++ b/include/jemalloc/internal/ticker.h @@ -1,6 +1,7 @@ #ifndef JEMALLOC_INTERNAL_TICKER_H #define JEMALLOC_INTERNAL_TICKER_H +#include "jemalloc/internal/prng.h" #include "jemalloc/internal/util.h" /** @@ -10,11 +11,11 @@ * have occurred with a call to ticker_ticks), which will return true (and reset * the counter) if the countdown hit zero. */ - -typedef struct { +typedef struct ticker_s ticker_t; +struct ticker_s { int32_t tick; int32_t nticks; -} ticker_t; +}; static inline void ticker_init(ticker_t *ticker, int32_t nticks) { @@ -75,7 +76,7 @@ ticker_tick(ticker_t *ticker) { return ticker_ticks(ticker, 1); } -/* +/* * Try to tick. If ticker would fire, return true, but rely on * slowpath to reset ticker. */ @@ -88,4 +89,87 @@ ticker_trytick(ticker_t *ticker) { return false; } +/* + * The ticker_geom_t is much like the ticker_t, except that instead of ticker + * having a constant countdown, it has an approximate one; each tick has + * approximately a 1/nticks chance of triggering the count. + * + * The motivation is in triggering arena decay. With a naive strategy, each + * thread would maintain a ticker per arena, and check if decay is necessary + * each time that the arena's ticker fires. This has two costs: + * - Since under reasonable assumptions both threads and arenas can scale + * linearly with the number of CPUs, maintaining per-arena data in each thread + * scales quadratically with the number of CPUs. + * - These tickers are often a cache miss down tcache flush pathways. + * + * By giving each tick a 1/nticks chance of firing, we still maintain the same + * average number of ticks-until-firing per arena, with only a single ticker's + * worth of metadata. + */ + +/* See ticker.c for an explanation of these constants. */ +#define TICKER_GEOM_NBITS 6 +#define TICKER_GEOM_MUL 61 +extern const uint8_t ticker_geom_table[1 << TICKER_GEOM_NBITS]; + +/* Not actually any different from ticker_t; just for type safety. */ +typedef struct ticker_geom_s ticker_geom_t; +struct ticker_geom_s { + int32_t tick; + int32_t nticks; +}; + +/* + * Just pick the average delay for the first counter. We're more concerned with + * the behavior over long periods of time rather than the exact timing of the + * initial ticks. + */ +#define TICKER_GEOM_INIT(nticks) {nticks, nticks} + +static inline void +ticker_geom_init(ticker_geom_t *ticker, int32_t nticks) { + /* + * Make sure there's no overflow possible. This shouldn't really be a + * problem for reasonable nticks choices, which are all static and + * relatively small. + */ + assert((uint64_t)nticks * (uint64_t)255 / (uint64_t)TICKER_GEOM_MUL + <= (uint64_t)INT32_MAX); + ticker->tick = nticks; + ticker->nticks = nticks; +} + +static inline int32_t +ticker_geom_read(const ticker_geom_t *ticker) { + return ticker->tick; +} + +/* Same deal as above. */ +#if defined(__GNUC__) && !defined(__clang__) \ + && (defined(__x86_64__) || defined(__i386__)) +JEMALLOC_NOINLINE +#endif +static bool +ticker_geom_fixup(ticker_geom_t *ticker, uint64_t *prng_state) { + uint64_t idx = prng_lg_range_u64(prng_state, TICKER_GEOM_NBITS); + ticker->tick = (uint32_t)( + (uint64_t)ticker->nticks * (uint64_t)ticker_geom_table[idx] + / (uint64_t)TICKER_GEOM_MUL); + return true; +} + +static inline bool +ticker_geom_ticks(ticker_geom_t *ticker, uint64_t *prng_state, int32_t nticks) { + ticker->tick -= nticks; + if (unlikely(ticker->tick < 0)) { + return ticker_geom_fixup(ticker, prng_state); + } + return false; +} + +static inline bool +ticker_geom_tick(ticker_geom_t *ticker, uint64_t *prng_state) { + return ticker_geom_ticks(ticker, prng_state, 1); +} + #endif /* JEMALLOC_INTERNAL_TICKER_H */ |