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store: 'mcached' users can specify a cache ID.

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Users of 'mcached' can now specify a cache ID; furthermore, the cache
hit rate is automatically recorded for all the caches accessed with
'mcached'.

* guix/store.scm (%max-store-connection-caches)
(%store-connection-cache-names): New variables.
(recorder-for-cache): New procedure.
(record-cache-lookup!): Add 'cache-id' parameter and rewrite in terms of
'recorder-for-cache'.
(lookup-cached-object): Add 'cache-id' parameter and honor it.
(%mcached): Add #:cache parameter and honor it.
(mcached): Add '=>' keyword and corresponding clauses.
This commit is contained in:
Ludovic Courtès 2022-05-12 23:16:11 +02:00
parent 3ae7632ca0
commit ba6ba1a5af
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GPG key ID: 090B11993D9AEBB5
1 changed files with 53 additions and 12 deletions
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65
guix/store.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2012-2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2018 Jan Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2019, 2020 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2020 Florian Pelz <pelzflorian@pelzflorian.de>
@ -1793,6 +1793,14 @@ (define-operation (clear-failed-paths (store-path-list items))
;; the 'caches' vector of <store-connection>.
(define %store-connection-caches (make-atomic-box 0))
(define %max-store-connection-caches
;; Maximum number of caches returned by 'allocate-store-connection-cache'.
32)
(define %store-connection-cache-names
;; Mapping of cache ID to symbol.
(make-vector %max-store-connection-caches))
(define (allocate-store-connection-cache name)
"Allocate a new cache for store connections and return its identifier. Said
identifier can be passed as an argument to "
@ -1800,7 +1808,9 @@ (define (allocate-store-connection-cache name)
(let ((previous (atomic-box-compare-and-swap! %store-connection-caches
current (+ current 1))))
(if (= previous current)
current
(begin
(vector-set! %store-connection-cache-names current name)
current)
(loop current)))))
(define %object-cache-id
@ -1926,16 +1936,37 @@ (define (cache-lookup-recorder component title)
(lambda (x y)
#t)))
(define record-cache-lookup!
(cache-lookup-recorder "object-cache" "Store object cache"))
(define recorder-for-cache
(let ((recorders (make-vector %max-store-connection-caches)))
(lambda (cache-id)
"Return a procedure to record lookup stats for CACHE-ID."
(match (vector-ref recorders cache-id)
((? unspecified?)
(let* ((name (symbol->string
(vector-ref %store-connection-cache-names cache-id)))
(description
(string-titlecase
(string-map (match-lambda
(#\- #\space)
(chr chr))
name))))
(let ((proc (cache-lookup-recorder name description)))
(vector-set! recorders cache-id proc)
proc)))
(proc proc)))))
(define-inlinable (lookup-cached-object object keys vhash-fold*)
"Return the cached object in the store connection corresponding to OBJECT
(define (record-cache-lookup! cache-id value cache)
"Record the lookup of VALUE in CACHE-ID, whose current value is CACHE."
(let ((record! (recorder-for-cache cache-id)))
(record! value cache)))
(define-inlinable (lookup-cached-object cache-id object keys vhash-fold*)
"Return the object in store cache CACHE-ID corresponding to OBJECT
and KEYS; use VHASH-FOLD* to look for OBJECT in the cache. KEYS is a list of
additional keys to match against, and which are compared with 'equal?'.
Return #f on failure and the cached result otherwise."
(lambda (store)
(let* ((cache (store-connection-cache store %object-cache-id))
(let* ((cache (store-connection-cache store cache-id))
;; Escape as soon as we find the result. This avoids traversing
;; the whole vlist chain and significantly reduces the number of
@ -1949,40 +1980,50 @@ (define-inlinable (lookup-cached-object object keys vhash-fold*)
result))))
#f object
cache))))
(record-cache-lookup! value cache)
(record-cache-lookup! cache-id value cache)
(values value store))))
(define* (%mcached mthunk object #:optional (keys '())
#:key
(cache %object-cache-id)
(vhash-cons vhash-consq)
(vhash-fold* vhash-foldq*))
"Bind the monadic value returned by MTHUNK, which supposedly corresponds to
OBJECT/KEYS, or return its cached value. Use VHASH-CONS to insert OBJECT into
the cache, and VHASH-FOLD* to look it up."
(mlet %store-monad ((cached (lookup-cached-object object keys
(mlet %store-monad ((cached (lookup-cached-object cache object keys
vhash-fold*)))
(if cached
(return cached)
(>>= (mthunk)
(lambda (result)
(cache-object-mapping object keys result
#:cache cache
#:vhash-cons vhash-cons))))))
(define-syntax mcached
(syntax-rules (eq? equal?)
(syntax-rules (eq? equal? =>)
"Run MVALUE, which corresponds to OBJECT/KEYS, and cache it; or return the
value associated with OBJECT/KEYS in the store's object cache if there is
one."
((_ eq? mvalue object keys ...)
((_ eq? (=> cache) mvalue object keys ...)
(%mcached (lambda () mvalue)
object (list keys ...)
#:cache cache
#:vhash-cons vhash-consq
#:vhash-fold* vhash-foldq*))
((_ equal? mvalue object keys ...)
((_ equal? (=> cache) mvalue object keys ...)
(%mcached (lambda () mvalue)
object (list keys ...)
#:cache cache
#:vhash-cons vhash-cons
#:vhash-fold* vhash-fold*))
((_ eq? mvalue object keys ...)
(mcached eq? (=> %object-cache-id)
mvalue object keys ...))
((_ equal? mvalue object keys ...)
(mcached equal? (=> %object-cache-id)
mvalue object keys ...))
((_ mvalue object keys ...)
(mcached eq? mvalue object keys ...))))