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Diffstat (limited to 'deps/jemalloc/src/thread_event.c')
| -rw-r--r-- | deps/jemalloc/src/thread_event.c | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/deps/jemalloc/src/thread_event.c b/deps/jemalloc/src/thread_event.c new file mode 100644 index 000000000..37eb5827d --- /dev/null +++ b/deps/jemalloc/src/thread_event.c @@ -0,0 +1,343 @@ +#include "jemalloc/internal/jemalloc_preamble.h" +#include "jemalloc/internal/jemalloc_internal_includes.h" + +#include "jemalloc/internal/thread_event.h" + +/* + * Signatures for event specific functions. These functions should be defined + * by the modules owning each event. The signatures here verify that the + * definitions follow the right format. + * + * The first two are functions computing new / postponed event wait time. New + * event wait time is the time till the next event if an event is currently + * being triggered; postponed event wait time is the time till the next event + * if an event should be triggered but needs to be postponed, e.g. when the TSD + * is not nominal or during reentrancy. + * + * The third is the event handler function, which is called whenever an event + * is triggered. The parameter is the elapsed time since the last time an + * event of the same type was triggered. + */ +#define E(event, condition_unused, is_alloc_event_unused) \ +uint64_t event##_new_event_wait(tsd_t *tsd); \ +uint64_t event##_postponed_event_wait(tsd_t *tsd); \ +void event##_event_handler(tsd_t *tsd, uint64_t elapsed); + +ITERATE_OVER_ALL_EVENTS +#undef E + +/* Signatures for internal functions fetching elapsed time. */ +#define E(event, condition_unused, is_alloc_event_unused) \ +static uint64_t event##_fetch_elapsed(tsd_t *tsd); + +ITERATE_OVER_ALL_EVENTS +#undef E + +static uint64_t +tcache_gc_fetch_elapsed(tsd_t *tsd) { + return TE_INVALID_ELAPSED; +} + +static uint64_t +tcache_gc_dalloc_fetch_elapsed(tsd_t *tsd) { + return TE_INVALID_ELAPSED; +} + +static uint64_t +prof_sample_fetch_elapsed(tsd_t *tsd) { + uint64_t last_event = thread_allocated_last_event_get(tsd); + uint64_t last_sample_event = prof_sample_last_event_get(tsd); + prof_sample_last_event_set(tsd, last_event); + return last_event - last_sample_event; +} + +static uint64_t +stats_interval_fetch_elapsed(tsd_t *tsd) { + uint64_t last_event = thread_allocated_last_event_get(tsd); + uint64_t last_stats_event = stats_interval_last_event_get(tsd); + stats_interval_last_event_set(tsd, last_event); + return last_event - last_stats_event; +} + +static uint64_t +peak_alloc_fetch_elapsed(tsd_t *tsd) { + return TE_INVALID_ELAPSED; +} + +static uint64_t +peak_dalloc_fetch_elapsed(tsd_t *tsd) { + return TE_INVALID_ELAPSED; +} + +/* Per event facilities done. */ + +static bool +te_ctx_has_active_events(te_ctx_t *ctx) { + assert(config_debug); +#define E(event, condition, alloc_event) \ + if (condition && alloc_event == ctx->is_alloc) { \ + return true; \ + } + ITERATE_OVER_ALL_EVENTS +#undef E + return false; +} + +static uint64_t +te_next_event_compute(tsd_t *tsd, bool is_alloc) { + uint64_t wait = TE_MAX_START_WAIT; +#define E(event, condition, alloc_event) \ + if (is_alloc == alloc_event && condition) { \ + uint64_t event_wait = \ + event##_event_wait_get(tsd); \ + assert(event_wait <= TE_MAX_START_WAIT); \ + if (event_wait > 0U && event_wait < wait) { \ + wait = event_wait; \ + } \ + } + + ITERATE_OVER_ALL_EVENTS +#undef E + assert(wait <= TE_MAX_START_WAIT); + return wait; +} + +static void +te_assert_invariants_impl(tsd_t *tsd, te_ctx_t *ctx) { + uint64_t current_bytes = te_ctx_current_bytes_get(ctx); + uint64_t last_event = te_ctx_last_event_get(ctx); + uint64_t next_event = te_ctx_next_event_get(ctx); + uint64_t next_event_fast = te_ctx_next_event_fast_get(ctx); + + assert(last_event != next_event); + if (next_event > TE_NEXT_EVENT_FAST_MAX || !tsd_fast(tsd)) { + assert(next_event_fast == 0U); + } else { + assert(next_event_fast == next_event); + } + + /* The subtraction is intentionally susceptible to underflow. */ + uint64_t interval = next_event - last_event; + + /* The subtraction is intentionally susceptible to underflow. */ + assert(current_bytes - last_event < interval); + uint64_t min_wait = te_next_event_compute(tsd, te_ctx_is_alloc(ctx)); + /* + * next_event should have been pushed up only except when no event is + * on and the TSD is just initialized. The last_event == 0U guard + * below is stronger than needed, but having an exactly accurate guard + * is more complicated to implement. + */ + assert((!te_ctx_has_active_events(ctx) && last_event == 0U) || + interval == min_wait || + (interval < min_wait && interval == TE_MAX_INTERVAL)); +} + +void +te_assert_invariants_debug(tsd_t *tsd) { + te_ctx_t ctx; + te_ctx_get(tsd, &ctx, true); + te_assert_invariants_impl(tsd, &ctx); + + te_ctx_get(tsd, &ctx, false); + te_assert_invariants_impl(tsd, &ctx); +} + +/* + * Synchronization around the fast threshold in tsd -- + * There are two threads to consider in the synchronization here: + * - The owner of the tsd being updated by a slow path change + * - The remote thread, doing that slow path change. + * + * As a design constraint, we want to ensure that a slow-path transition cannot + * be ignored for arbitrarily long, and that if the remote thread causes a + * slow-path transition and then communicates with the owner thread that it has + * occurred, then the owner will go down the slow path on the next allocator + * operation (so that we don't want to just wait until the owner hits its slow + * path reset condition on its own). + * + * Here's our strategy to do that: + * + * The remote thread will update the slow-path stores to TSD variables, issue a + * SEQ_CST fence, and then update the TSD next_event_fast counter. The owner + * thread will update next_event_fast, issue an SEQ_CST fence, and then check + * its TSD to see if it's on the slow path. + + * This is fairly straightforward when 64-bit atomics are supported. Assume that + * the remote fence is sandwiched between two owner fences in the reset pathway. + * The case where there is no preceding or trailing owner fence (i.e. because + * the owner thread is near the beginning or end of its life) can be analyzed + * similarly. The owner store to next_event_fast preceding the earlier owner + * fence will be earlier in coherence order than the remote store to it, so that + * the owner thread will go down the slow path once the store becomes visible to + * it, which is no later than the time of the second fence. + + * The case where we don't support 64-bit atomics is trickier, since word + * tearing is possible. We'll repeat the same analysis, and look at the two + * owner fences sandwiching the remote fence. The next_event_fast stores done + * alongside the earlier owner fence cannot overwrite any of the remote stores + * (since they precede the earlier owner fence in sb, which precedes the remote + * fence in sc, which precedes the remote stores in sb). After the second owner + * fence there will be a re-check of the slow-path variables anyways, so the + * "owner will notice that it's on the slow path eventually" guarantee is + * satisfied. To make sure that the out-of-band-messaging constraint is as well, + * note that either the message passing is sequenced before the second owner + * fence (in which case the remote stores happen before the second set of owner + * stores, so malloc sees a value of zero for next_event_fast and goes down the + * slow path), or it is not (in which case the owner sees the tsd slow-path + * writes on its previous update). This leaves open the possibility that the + * remote thread will (at some arbitrary point in the future) zero out one half + * of the owner thread's next_event_fast, but that's always safe (it just sends + * it down the slow path earlier). + */ +static void +te_ctx_next_event_fast_update(te_ctx_t *ctx) { + uint64_t next_event = te_ctx_next_event_get(ctx); + uint64_t next_event_fast = (next_event <= TE_NEXT_EVENT_FAST_MAX) ? + next_event : 0U; + te_ctx_next_event_fast_set(ctx, next_event_fast); +} + +void +te_recompute_fast_threshold(tsd_t *tsd) { + if (tsd_state_get(tsd) != tsd_state_nominal) { + /* Check first because this is also called on purgatory. */ + te_next_event_fast_set_non_nominal(tsd); + return; + } + + te_ctx_t ctx; + te_ctx_get(tsd, &ctx, true); + te_ctx_next_event_fast_update(&ctx); + te_ctx_get(tsd, &ctx, false); + te_ctx_next_event_fast_update(&ctx); + + atomic_fence(ATOMIC_SEQ_CST); + if (tsd_state_get(tsd) != tsd_state_nominal) { + te_next_event_fast_set_non_nominal(tsd); + } +} + +static void +te_adjust_thresholds_helper(tsd_t *tsd, te_ctx_t *ctx, + uint64_t wait) { + /* + * The next threshold based on future events can only be adjusted after + * progressing the last_event counter (which is set to current). + */ + assert(te_ctx_current_bytes_get(ctx) == te_ctx_last_event_get(ctx)); + assert(wait <= TE_MAX_START_WAIT); + + uint64_t next_event = te_ctx_last_event_get(ctx) + (wait <= + TE_MAX_INTERVAL ? wait : TE_MAX_INTERVAL); + te_ctx_next_event_set(tsd, ctx, next_event); +} + +static uint64_t +te_clip_event_wait(uint64_t event_wait) { + assert(event_wait > 0U); + if (TE_MIN_START_WAIT > 1U && + unlikely(event_wait < TE_MIN_START_WAIT)) { + event_wait = TE_MIN_START_WAIT; + } + if (TE_MAX_START_WAIT < UINT64_MAX && + unlikely(event_wait > TE_MAX_START_WAIT)) { + event_wait = TE_MAX_START_WAIT; + } + return event_wait; +} + +void +te_event_trigger(tsd_t *tsd, te_ctx_t *ctx) { + /* usize has already been added to thread_allocated. */ + uint64_t bytes_after = te_ctx_current_bytes_get(ctx); + /* The subtraction is intentionally susceptible to underflow. */ + uint64_t accumbytes = bytes_after - te_ctx_last_event_get(ctx); + + te_ctx_last_event_set(ctx, bytes_after); + + bool allow_event_trigger = tsd_nominal(tsd) && + tsd_reentrancy_level_get(tsd) == 0; + bool is_alloc = ctx->is_alloc; + uint64_t wait = TE_MAX_START_WAIT; + +#define E(event, condition, alloc_event) \ + bool is_##event##_triggered = false; \ + if (is_alloc == alloc_event && condition) { \ + uint64_t event_wait = event##_event_wait_get(tsd); \ + assert(event_wait <= TE_MAX_START_WAIT); \ + if (event_wait > accumbytes) { \ + event_wait -= accumbytes; \ + } else if (!allow_event_trigger) { \ + event_wait = event##_postponed_event_wait(tsd); \ + } else { \ + is_##event##_triggered = true; \ + event_wait = event##_new_event_wait(tsd); \ + } \ + event_wait = te_clip_event_wait(event_wait); \ + event##_event_wait_set(tsd, event_wait); \ + if (event_wait < wait) { \ + wait = event_wait; \ + } \ + } + + ITERATE_OVER_ALL_EVENTS +#undef E + + assert(wait <= TE_MAX_START_WAIT); + te_adjust_thresholds_helper(tsd, ctx, wait); + te_assert_invariants(tsd); + +#define E(event, condition, alloc_event) \ + if (is_alloc == alloc_event && condition && \ + is_##event##_triggered) { \ + assert(allow_event_trigger); \ + uint64_t elapsed = event##_fetch_elapsed(tsd); \ + event##_event_handler(tsd, elapsed); \ + } + + ITERATE_OVER_ALL_EVENTS +#undef E + + te_assert_invariants(tsd); +} + +static void +te_init(tsd_t *tsd, bool is_alloc) { + te_ctx_t ctx; + te_ctx_get(tsd, &ctx, is_alloc); + /* + * Reset the last event to current, which starts the events from a clean + * state. This is necessary when re-init the tsd event counters. + * + * The event counters maintain a relationship with the current bytes: + * last_event <= current < next_event. When a reinit happens (e.g. + * reincarnated tsd), the last event needs progressing because all + * events start fresh from the current bytes. + */ + te_ctx_last_event_set(&ctx, te_ctx_current_bytes_get(&ctx)); + + uint64_t wait = TE_MAX_START_WAIT; +#define E(event, condition, alloc_event) \ + if (is_alloc == alloc_event && condition) { \ + uint64_t event_wait = event##_new_event_wait(tsd); \ + event_wait = te_clip_event_wait(event_wait); \ + event##_event_wait_set(tsd, event_wait); \ + if (event_wait < wait) { \ + wait = event_wait; \ + } \ + } + + ITERATE_OVER_ALL_EVENTS +#undef E + te_adjust_thresholds_helper(tsd, &ctx, wait); +} + +void +tsd_te_init(tsd_t *tsd) { + /* Make sure no overflow for the bytes accumulated on event_trigger. */ + assert(TE_MAX_INTERVAL <= UINT64_MAX - SC_LARGE_MAXCLASS + 1); + te_init(tsd, true); + te_init(tsd, false); + te_assert_invariants(tsd); +} |