feat(scheduler-core): implement clock virtualization and session timing (task 4.5)
Adds xce_core_now() (new core_clock.c, kept separate from core.c so test_core_isolation.c's wall-clock scan still enforces zero direct clock_gettime()/time() calls elsewhere in the core): the two-anchor plus speed formula (virtual_clock_base + (elapsed * speed_num) / speed_den), covering all four modes (normal, discrete/real-time/fast- slow simulation) via four new atomic fields on xce_sched_core_t, defaulted to normal-mode (1/1 speed) in xce_sched_core_init(). requirements.md's literal tlog_reg_format_func(fn, core_ptr) call shape doesn't exist in the real vendored tlog library (registration takes only the callback; userptr is per-call-site, not bindable at registration) -- resolved with a module-level active-core pointer read by a new core-scoped format function, not wired into mylog_init()/ main.c yet. xce_core_go()/xce_core_end_session() (task 4.4) now stamp session_start/compute session_duration_ns via xce_core_now(), with their existing session-active/reentrancy behavior untouched. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019dw5WnN3DXStaEaPYfACU1
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9 changed files with 849 additions and 5 deletions
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@ -23,6 +23,19 @@
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* testsuite/test_core_isolation.c (source-text scan + an nm(1) undefined-
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* symbol audit of core.c's compiled object, the build-time proof this
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* task's Observable requires).
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*
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* One documented exception (task 4.5, Req 5 AC 3): the core's single
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* sanctioned wall-clock call -- clock_gettime(CLOCK_MONOTONIC) inside
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* xce_core_now() -- and its tlog format-function integration live in
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* core_clock.c, a SEPARATE file from core.c, specifically so
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* test_core_isolation.c's core.c-scoped "zero wall-clock calls" text scan
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* keeps proving what it has always proven (core.c itself never reads real
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* time) without needing to special-case the one legitimate call site AC 3
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* mandates. tlog (tinylog) is likewise an allowed core dependency as of
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* this task -- AC 3's own "Third-party library constraint" section
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* discusses the core registering a tlog format function -- distinct from
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* the forbidden client.h/netio.h/xceapi.h/delay.h/idgen.h/xce/cluster.h
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* list above, none of which tlog is part of.
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*/
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#include <pthread.h>
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@ -102,6 +115,55 @@ struct xce_sched_core_s {
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_Atomic int staging_merge_complete; /* 1 after staging merge completes */
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select_eval_ctx_t* sel_eval_ctx; /* session-level memoisation context; NULL
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between sessions */
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/*
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* Clock virtualization (Req 5 AC 3, scheduler-core spec, task 4.5): the
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* core's ONLY sanctioned time source is xce_core_now() (core_clock.c),
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* which computes virtual time from these four fields via the
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* two-anchor + speed formula:
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*
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* wall_ns = clock_gettime(CLOCK_MONOTONIC) // the one wall-clock
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* // call in the whole
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* // core -- lives in
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* // core_clock.c, NOT
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* // core.c (core.c's own
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* // zero-wall-clock
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* // guarantee, enforced
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* // by
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* // test_core_isolation.c,
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* // stays intact)
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* elapsed = wall_ns - real_clock_base
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* xce_core_now() = virtual_clock_base + (elapsed * speed_num) / speed_den
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*
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* Atomically updated by the driver AS A GROUP before each event
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* dispatch (design.md's State Management note) -- xce_core_now() reads
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* them lock-free, no mutex, safe from both the picker and allocator
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* threads. xce_sched_core_init() seeds these to AC 3's Normal-mode row
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* (virtual_clock_base=0, real_clock_base=0, speed_num=1, speed_den=1):
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* degraded-to-real-wall-clock default, today's existing production
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* behavior, preserved until a future simulation driver (Phase 3)
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* explicitly reconfigures them.
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*/
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_Atomic uint64_t virtual_clock_base;
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_Atomic uint64_t real_clock_base;
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_Atomic uint64_t speed_num;
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_Atomic uint64_t speed_den;
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/*
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* Session response-time diagnostics (Req 5 AC 12, task 4.5). Plain
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* (non-atomic) fields -- touched only by the driver thread, inside
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* xce_core_go()/xce_core_end_session() (core_session.c), the same
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* single-writer discipline core->sel_eval_ctx above already follows.
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* session_start is stamped at the top of xce_core_go(); the field name
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* matches requirements.md's own pseudocode verbatim
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* ("session_start = xce_core_now()"). session_duration_ns is computed
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* at the top of xce_core_end_session() as xce_core_now() -
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* session_start. Both are diagnostics only -- nothing in the
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* scheduling/decision path reads them. The ReplaySession.summary
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* SessionSummary wire struct these values eventually feed is explicitly
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* OUT of this task's scope (Phase 3, recording/replay-format tasks
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* 7.x) -- this struct only holds the plain numeric tracking.
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*/
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uint64_t session_start;
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uint64_t session_duration_ns;
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};
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/*
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@ -302,4 +364,40 @@ extern int xce_core_go(xce_sched_core_t*);
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*/
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extern int xce_core_end_session(xce_sched_core_t*);
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/*
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* xce_core_now - Req 5 AC 3 (scheduler-core spec, task 4.5): the core's
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* virtualized clock accessor, and the ONLY place inside the scheduler-core
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* module family that calls clock_gettime() (implemented in core_clock.c,
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* deliberately NOT core.c -- see this header's own top-of-file boundary
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* comment and xce_sched_core_t's clock-field doc comment above for why).
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* Computes virtual time via the two-anchor + speed formula from
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* virtual_clock_base/real_clock_base/speed_num/speed_den, reading all four
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* atomically (lock-free, safe from any thread). Returns 0 if core is NULL.
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*/
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extern uint64_t xce_core_now(xce_sched_core_t*);
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/*
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* xce_core_set_active_for_logging / xce_core_register_tlog_format - Req 5
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* AC 3's tlog integration (task 4.5). See core_clock.c's own file header
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* comment for the full reasoning behind this exact mechanism, including why
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* it deliberately does NOT match AC 3's literal
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* `tlog_reg_format_func(fn, core_ptr)` pseudocode -- that call shape does
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* not exist in the real vendored tlog.h (`tlog_reg_format_func()` takes
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* only the callback, no userptr-binding parameter; userptr is a per-call-
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* site argument that flows through tlog_ext()/tlog_vext(), not something
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* bindable once at registration time).
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*
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* xce_core_set_active_for_logging(core) sets (or, passed NULL, clears) a
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* module-level "active core for logging" pointer that core_clock.c's
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* registered tlog_format_func reads via xce_core_now() instead of
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* info->time. xce_core_register_tlog_format() registers that format
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* function with tlog via the real tlog_reg_format_func(). Neither is
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* called from mylog_init()/main.c by this task -- wiring the live
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* scheduler process over to this mechanism is a later task's job,
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* consistent with tasks 4.1-4.4's additive-only, unwired-until-a-driver-
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* exists pattern.
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*/
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extern void xce_core_set_active_for_logging(xce_sched_core_t*);
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extern int xce_core_register_tlog_format(void);
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#endif
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