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Three primitives + a wrapper, all portable across hosts: with-jit-threshold N body... — temporarily set threshold, restore on exit with-jit-budget N body... — temporarily set LRU budget with-fresh-jit body... — clear cache before & after body jit-report — human-readable stats string for logging jit-disable! / jit-enable! — convenience around set-budget! 0 The host (OCaml here, will be JS/Python eventually) only needs to provide the underlying primitives (jit-stats, jit-set-threshold!, jit-set-budget!, jit-reset-cache!, jit-reset-counters!). The ergonomics live in shared SX. Used together with Phase 1 (tiered compilation) and Phase 2 (LRU eviction) to give application developers fine-grained control over the JIT cache: isolated test runs use with-fresh-jit, hot benchmark sections use with-jit-threshold 1, memory-constrained pages use jit-set-budget! to cap the cache. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
90 lines
2.8 KiB
Plaintext
90 lines
2.8 KiB
Plaintext
;; lib/jit.sx — SX-level convenience wrappers over the JIT cache control
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;; primitives (jit-stats, jit-set-threshold!, jit-set-budget!, jit-reset-cache!,
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;; jit-reset-counters!). Host-specific implementations live in
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;; hosts/<host>/lib/sx_*.ml; the API surface is portable across hosts.
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;; with-jit-threshold — temporarily set the JIT call-count threshold for
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;; the duration of body, restoring the previous value on exit. Useful for
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;; sections that want eager compilation (threshold=1) or want to skip JIT
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;; entirely (threshold=999999) for diagnostic comparison.
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(defmacro
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with-jit-threshold
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(n &rest body)
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`(let
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((__old (get (jit-stats) "threshold")))
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(jit-set-threshold! ,n)
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(let
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((__r (do ,@body)))
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(jit-set-threshold! __old)
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__r)))
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;; with-jit-budget — temporarily set the LRU cache budget. Setting to 0
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;; disables JIT entirely (everything falls through to the interpreter);
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;; large values are effectively unbounded.
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(defmacro
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with-jit-budget
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(n &rest body)
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`(let
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((__old (get (jit-stats) "budget")))
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(jit-set-budget! ,n)
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(let
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((__r (do ,@body)))
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(jit-set-budget! __old)
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__r)))
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;; with-fresh-jit — clear the cache before body, run body, clear again
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;; after. Use between sessions / request batches / test suites where you
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;; want deterministic timing free of carryover.
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(defmacro
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with-fresh-jit
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(&rest body)
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`(let
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((__r (do (jit-reset-cache!) ,@body)))
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(jit-reset-cache!)
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__r))
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;; jit-report — human-readable summary of current JIT state. Returns a
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;; string suitable for logging.
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(define
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jit-report
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(fn
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()
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(let
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((s (jit-stats)))
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(let
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((compiled (get s "compiled"))
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(skipped (get s "below-threshold"))
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(failed (get s "compile-failed"))
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(evicted (get s "evicted"))
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(cache-size (get s "cache-size"))
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(budget (get s "budget"))
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(threshold (get s "threshold")))
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(let
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((total (+ compiled skipped failed)))
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(str
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"jit: " cache-size "/" budget " cached "
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"(thr=" threshold ") · "
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compiled " compiled, "
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skipped " below-thr, "
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failed " failed, "
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evicted " evicted "
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"(" (if (> total 0) (* 100 (/ compiled total)) 0) "% compile rate)"))))))
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;; jit-disable! / jit-enable! — convenience helpers. Disabling sets budget
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;; to 0 which causes the VM to skip JIT entirely on the next call. Enable
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;; restores the budget to its previous value (or 5000 if no previous).
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(define _jit-saved-budget (list 5000))
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(define
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jit-disable!
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(fn
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()
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(set! _jit-saved-budget (list (get (jit-stats) "budget")))
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(jit-set-budget! 0)))
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(define
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jit-enable!
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(fn
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()
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(jit-set-budget! (first _jit-saved-budget))))
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