X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fpcl%2Fcache.lisp;h=f70a2a8f8ac8f6e2350423a90357c0077896964b;hb=bfb19d306581ac86feb4371846c4b9953d692dd8;hp=196b57ad2d97f55811c0048955b9bb853fc10386;hpb=562e48a2bd3467121e24214110e535c841fbb622;p=sbcl.git diff --git a/src/pcl/cache.lisp b/src/pcl/cache.lisp index 196b57a..f70a2a8 100644 --- a/src/pcl/cache.lisp +++ b/src/pcl/cache.lisp @@ -81,20 +81,49 @@ ;; (mod index (length vector)) ;; using a bitmask. (vector #() :type simple-vector) - ;; The bitmask used to calculate (mod index (length vector))l + ;; The bitmask used to calculate + ;; (mod (* line-size line-hash) (length vector))). (mask 0 :type fixnum) ;; Current probe-depth needed in the cache. (depth 0 :type index) ;; Maximum allowed probe-depth before the cache needs to expand. (limit 0 :type index)) +(defun compute-cache-mask (vector-length line-size) + ;; Since both vector-length and line-size are powers of two, we + ;; can compute a bitmask such that + ;; + ;; (logand ) + ;; + ;; is "morally equal" to + ;; + ;; (mod (* ) ) + ;; + ;; This is it: (1- vector-length) is #b111... of the approriate size + ;; to get the MOD, and (- line-size) gives right the number of zero + ;; bits at the low end. + (logand (1- vector-length) (- line-size))) + ;;; The smallest power of two that is equal to or greater then X. (declaim (inline power-of-two-ceiling)) (defun power-of-two-ceiling (x) (ash 1 (integer-length (1- x)))) -;;; Don't allocate insanely huge caches. -(defconstant +cache-vector-max-length+ (expt 2 14)) +(defun cache-statistics (cache) + (let* ((vector (cache-vector cache)) + (size (length vector)) + (line-size (cache-line-size cache)) + (total-lines (/ size line-size)) + (free-lines (loop for i from 0 by line-size below size + unless (eq (svref vector i) '..empty..) + count t))) + (values (- total-lines free-lines) total-lines + (cache-depth cache) (cache-limit cache)))) + +;;; Don't allocate insanely huge caches: this is 4096 lines for a +;;; value cache with 8-15 keys -- probably "big enough for anyone", +;;; and 16384 lines for a commonplace 2-key value cache. +(defconstant +cache-vector-max-length+ (expt 2 16)) ;;; Compute the maximum allowed probe depth as a function of cache size. ;;; Cache size refers to number of cache lines, not the length of the @@ -104,7 +133,7 @@ ;;; policy into account here (speed vs. space.) (declaim (inline compute-limit)) (defun compute-limit (size) - (ceiling (sqrt size) 2)) + (ceiling (sqrt (sqrt size)))) ;;; Returns VALUE if it is not ..EMPTY.., otherwise executes ELSE: (defmacro non-empty-or (value else) @@ -120,22 +149,6 @@ (defun cache-key-p (thing) (not (symbolp thing))) -(eval-when (:compile-toplevel :load-toplevel :execute) - (sb-kernel:define-structure-slot-compare-and-swap compare-and-swap-cache-depth - :structure cache - :slot depth)) - -;;; Utility macro for atomic updates without locking... doesn't -;;; do much right now, and it would be nice to make this more magical. -(defmacro compare-and-swap (place old new) - (unless (consp place) - (error "Don't know how to compare and swap ~S." place)) - (ecase (car place) - (svref - `(simple-vector-compare-and-swap ,@(cdr place) ,old ,new)) - (cache-depth - `(compare-and-swap-cache-depth ,@(cdr place) ,old ,new)))) - ;;; Atomically update the current probe depth of a cache. (defun note-cache-depth (cache depth) (loop for old = (cache-depth cache) @@ -162,10 +175,11 @@ (defun compute-cache-index (cache layouts) (let ((index (hash-layout-or (car layouts) (return-from compute-cache-index nil)))) + (declare (fixnum index)) (dolist (layout (cdr layouts)) (mixf index (hash-layout-or layout (return-from compute-cache-index nil)))) ;; align with cache lines - (logand (* (cache-line-size cache) index) (cache-mask cache)))) + (logand index (cache-mask cache)))) ;;; Emit code that does lookup in cache bound to CACHE-VAR using ;;; layouts bound to LAYOUT-VARS. Go to MISS-TAG on event of a miss or @@ -181,16 +195,16 @@ (with-unique-names (n-index n-vector n-depth n-pointer n-mask MATCH-WRAPPERS EXIT-WITH-HIT) `(let* ((,n-index (hash-layout-or ,(car layout-vars) (go ,miss-tag))) - (,n-vector (cache-vector ,cache-var))) + (,n-vector (cache-vector ,cache-var)) + (,n-mask (cache-mask ,cache-var))) (declare (index ,n-index)) ,@(mapcar (lambda (layout-var) `(mixf ,n-index (hash-layout-or ,layout-var (go ,miss-tag)))) (cdr layout-vars)) ;; align with cache lines - (setf ,n-index (logand (* ,line-size ,n-index) (cache-mask ,cache-var))) + (setf ,n-index (logand ,n-index ,n-mask)) (let ((,n-depth (cache-depth ,cache-var)) - (,n-pointer ,n-index) - (,n-mask (cache-mask ,cache-var))) + (,n-pointer ,n-index)) (declare (index ,n-depth ,n-pointer)) (tagbody ,MATCH-WRAPPERS @@ -300,24 +314,32 @@ :line-size line-size :vector (make-array length :initial-element '..empty..) :value value - :mask (1- length) + :mask (compute-cache-mask length line-size) :limit (compute-limit adjusted-size)) ;; Make a smaller one, then (make-cache :key-count key-count :value value :size (ceiling size 2))))) ;;;; Copies and expands the cache, dropping any invalidated or ;;;; incomplete lines. -(defun copy-and-expand-cache (cache) +(defun copy-and-expand-cache (cache layouts value) (let ((copy (%copy-cache cache)) (length (length (cache-vector cache)))) (when (< length +cache-vector-max-length+) (setf length (* 2 length))) (tagbody :again - (setf (cache-vector copy) (make-array length :initial-element '..empty..) + ;; Blow way the old vector first, so a GC potentially triggered by + ;; MAKE-ARRAY can collect it. + (setf (cache-vector copy) #() + (cache-vector copy) (make-array length :initial-element '..empty..) (cache-depth copy) 0 - (cache-mask copy) (1- length) + (cache-mask copy) (compute-cache-mask length (cache-line-size cache)) (cache-limit copy) (compute-limit (/ length (cache-line-size cache)))) + ;; First insert the new one -- if we don't do this first and + ;; the cache has reached it's maximum size we may end up + ;; looping in FILL-CACHE. + (unless (try-update-cache copy layouts value) + (bug "Could not insert ~S:~S to supposedly empty ~S." layouts value cache)) (map-cache (lambda (layouts value) (unless (try-update-cache copy layouts value) ;; If the cache would grow too much we drop the @@ -335,11 +357,30 @@ copy)) (defun cache-has-invalid-entries-p (cache) - (and (find-if (lambda (elt) - (and (typep elt 'layout) - (zerop (layout-clos-hash elt)))) - (cache-vector cache)) - t)) + (let ((vector (cache-vector cache)) + (line-size (cache-line-size cache)) + (key-count (cache-key-count cache)) + (mask (cache-mask cache)) + (index 0)) + (loop + ;; Check if the line is in use, and check validity of the keys. + (let ((key1 (svref vector index))) + (when (cache-key-p key1) + (if (zerop (layout-clos-hash key1)) + ;; First key invalid. + (return-from cache-has-invalid-entries-p t) + ;; Line is in use and the first key is valid: check the rest. + (loop for offset from 1 below key-count + do (let ((thing (svref vector (+ index offset)))) + (when (or (not (cache-key-p thing)) + (zerop (layout-clos-hash thing))) + ;; Incomplete line or invalid layout. + (return-from cache-has-invalid-entries-p t))))))) + ;; Line empty of valid, onwards. + (setf index (next-cache-index mask index line-size)) + (when (zerop index) + ;; wrapped around + (return-from cache-has-invalid-entries-p nil))))) (defun hash-table-to-cache (table &key value key-count) (let ((cache (make-cache :key-count key-count :value value @@ -361,7 +402,7 @@ ;; we just drop the invalid entries. (%fill-cache (copy-cache cache) layouts value)) (t - (%fill-cache (copy-and-expand-cache cache) layouts value))))) + (copy-and-expand-cache cache layouts value))))) (if (listp layouts) (%fill-cache cache layouts value) (%fill-cache cache (list layouts) value)))) @@ -405,8 +446,8 @@ (line-size (cache-line-size cache)) (key-count (cache-key-count cache)) (valuep (cache-value cache)) - (size (/ (length vector) line-size)) (mask (cache-mask cache)) + (size (/ (length vector) line-size)) (index 0) (elt nil) (depth 0)) @@ -441,5 +482,33 @@ :key-count (cache-key-count cache) :line-size line-size :value valuep - :mask (cache-mask cache) + :mask mask :limit (cache-limit cache)))) + +;;;; For debugging & collecting statistics. + +(defun map-all-caches (function) + (dolist (p (list-all-packages)) + (do-symbols (s p) + (when (eq p (symbol-package s)) + (dolist (name (list s + `(setf ,s) + (slot-reader-name s) + (slot-writer-name s) + (slot-boundp-name s))) + (when (fboundp name) + (let ((fun (fdefinition name))) + (when (typep fun 'generic-function) + (let ((cache (gf-dfun-cache fun))) + (when cache + (funcall function name cache))))))))))) + +(defun check-cache-consistency (cache) + (let ((table (make-hash-table :test 'equal))) + (map-cache (lambda (layouts value) + (declare (ignore value)) + (if (gethash layouts table) + (cerror "Check futher." + "Multiple appearances of ~S." layouts) + (setf (gethash layouts table) t))) + cache)))