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in Protocols by
Currently `satisfies?` doesn't use the same impl cache used by protocol methods, making it too slow for real world usage.

With:

(defprotocol p (f [_]))
(deftype x [])
(deftype y [])
(extend-type x p (f [_]))


Before patch:

(let [s "abc"] (bench (instance? CharSequence s))) ;; Execution time mean : 1.358360 ns
(let [x (x.)] (bench (satisfies? p x))) ;; Execution time mean : 112.649568 ns
(let [y (y.)] (bench (satisfies? p y))) ;; Execution time mean : 2.605426 µs


*Cause:* `satisfies?` calls `find-protocol-impl` to see whether an object implements a protocol, which checks for whether x is an instance of the protocol interface or whether x's class is one of the protocol implementations (or if its in an inheritance chain that would make this true). This check is fairly expensive and not cached.

*Proposed:* Extend the protocol's method impl cache to also handle (and cache) instance checks (including negative results).

After patch:

(let [x (x.)] (bench (satisfies? p x))) ;; Execution time mean : 79.321426 ns
(let [y (y.)] (bench (satisfies? p y))) ;; Execution time mean : 77.410858 ns


*Patch*: CLJ-1814-v7.patch (depends on CLJ-2426)

25 Answers

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Comment made by: michaelblume

Nice. Honeysql used to spend 80-90% of its time in satisfies? calls before we refactored them out.

0 votes
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Comment made by: michaelblume

I realize this is a deeply annoying bug to reproduce, but if I clone core.match, point its Clojure dependency to 1.8.0-master-SNAPSHOT, start a REPL, connect to the REPL from vim, and reload clojure.core.match, I get

`
|| java.lang.Exception: namespace 'clojure.tools.analyzer.jvm.utils' not found, compiling:(clojure/tools/analyzer/jvm.clj:9:1)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5647| clojure.core$throw_if.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5733| clojure.core$load_lib.invokeStatic
|| clojure.core$load_lib.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:142)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5765| clojure.core$load_libs.invokeStatic
|| clojure.core$load_libs.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:137)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5787| clojure.core$require.invokeStatic
|| clojure.core$require.doInvoke(core.clj)
|| clojure.lang.RestFn.invoke(RestFn.java:703)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.analyzer.jvm/0.6.5/tools.analyzer.jvm-0.6.5.jar::clojure/tools/analyzer/jvm.clj|9| clojure.tools.analyzer.jvm$eval4968$loading5561auto__4969.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.analyzer.jvm/0.6.5/tools.analyzer.jvm-0.6.5.jar::clojure/tools/analyzer/jvm.clj|9| clojure.tools.analyzer.jvm$eval4968.invokeStatic
|| clojure.tools.analyzer.jvm$eval4968.invoke(jvm.clj)
|| clojure.lang.Compiler.eval(Compiler.java:6934)
|| clojure.lang.Compiler.eval(Compiler.java:6923)
|| clojure.lang.Compiler.load(Compiler.java:7381)
|| clojure.lang.RT.loadResourceScript(RT.java:372)
|| clojure.lang.RT.loadResourceScript(RT.java:363)
|| clojure.lang.RT.load(RT.java:453)
|| clojure.lang.RT.load(RT.java:419)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5883| clojure.core$load$fn
5669.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5882| clojure.core$load.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5683| clojure.core$load_one.invokeStatic
|| clojure.core$load_one.invoke(core.clj)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5728| clojure.core$load_lib$fn5618.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5727| clojure.core$load_lib.invokeStatic
|| clojure.core$load_lib.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:142)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5765| clojure.core$load_libs.invokeStatic
|| clojure.core$load_libs.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:137)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5787| clojure.core$require.invokeStatic
|| clojure.core$require.doInvoke(core.clj)
|| clojure.lang.RestFn.invoke(RestFn.java:457)
src/main/clojure/clojure/core/match.clj|1| clojure.core.match$eval4960$loading
5561auto__4961.invoke
src/main/clojure/clojure/core/match.clj|1| clojure.core.match$eval4960.invokeStatic
|| clojure.core.match$eval4960.invoke(match.clj)
|| clojure.lang.Compiler.eval(Compiler.java:6934)
|| clojure.lang.Compiler.eval(Compiler.java:6923)
|| clojure.lang.Compiler.load(Compiler.java:7381)
|| clojure.lang.RT.loadResourceScript(RT.java:372)
|| clojure.lang.RT.loadResourceScript(RT.java:363)
|| clojure.lang.RT.load(RT.java:453)
|| clojure.lang.RT.load(RT.java:419)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5883| clojure.core$load$fn5669.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5882| clojure.core$load.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5683| clojure.core$load_one.invokeStatic
|| clojure.core$load_one.invoke(core.clj)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5728| clojure.core$load_lib$fn5618.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5727| clojure.core$load_lib.invokeStatic
|| clojure.core$load_lib.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:142)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5765| clojure.core$load_libs.invokeStatic
|| clojure.core$load_libs.doInvoke(core.clj)
|| clojure.lang.RestFn.applyTo(RestFn.java:137)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5787| clojure.core$require.invokeStatic
|| clojure.core$require.doInvoke(core.clj)
|| clojure.lang.RestFn.invoke(RestFn.java:421)
|| clojure.core.match$eval4949.invokeStatic(form-init2494799382238714928.clj:1)
|| clojure.core.match$eval4949.invoke(form-init2494799382238714928.clj)
|| clojure.lang.Compiler.eval(Compiler.java:6934)
|| clojure.lang.Compiler.eval(Compiler.java:6897)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|3096| clojure.core$eval.invokeStatic
|| clojure.core$eval.invoke(core.clj)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|240| clojure.main$repl$read_eval_print
7404$fn7407.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|240| clojure.main$repl$read_eval_print
7404.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|258| clojure.main$repl$fn7413.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|258| clojure.main$repl.invokeStatic
|| clojure.main$repl.doInvoke(main.clj)
|| clojure.lang.RestFn.invoke(RestFn.java:1523)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|58| clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn
637.invoke
|| clojure.lang.AFn.applyToHelper(AFn.java:152)
|| clojure.lang.AFn.applyTo(AFn.java:144)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|645| clojure.core$apply.invokeStatic
zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|1874| clojure.core$with_bindingsSTAR.invokeStatic
|| clojure.core$with_bindingsSTAR.doInvoke(core.clj)
|| clojure.lang.RestFn.invoke(RestFn.java:425)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|56| clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invokeStatic
|| clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invoke(interruptible_eval.clj)
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|191| clojure.tools.nrepl.middleware.interruptible_eval$interruptible_eval$fn
679$fn__682.invoke
zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|159| clojure.tools.nrepl.middleware.interruptible_eval$run_next$fn__674.invoke
|| clojure.lang.AFn.run(AFn.java:22)
|| java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
|| java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
|| java.lang.Thread.run(Thread.java:745)

`

Same thing with reloading a namespace in my own project which depends on clojure.core.match

0 votes
by

Comment made by: bronsa

is it possible that AOT is involved?

0 votes
by

Comment made by: michaelblume

Narrowed it down a little, if I check out tools.analyzer.jvm, open a REPL, and do (require 'clojure.tools.analyzer.jvm.utils) I get

|| java.lang.ClassCastException: java.lang.Class cannot be cast to clojure.asm.Type, compiling:(utils.clj:260:13) || clojure.lang.Compiler$InvokeExpr.eval(Compiler.java:3642) || clojure.lang.Compiler$InvokeExpr.eval(Compiler.java:3636) || clojure.lang.Compiler$DefExpr.eval(Compiler.java:450) || clojure.lang.Compiler.eval(Compiler.java:6939) || clojure.lang.Compiler.load(Compiler.java:7381) || clojure.lang.RT.loadResourceScript(RT.java:372) || clojure.lang.RT.loadResourceScript(RT.java:363) || clojure.lang.RT.load(RT.java:453) || clojure.lang.RT.load(RT.java:419) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5883| clojure.core$load$fn__5669.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5882| clojure.core$load.invokeStatic zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5683| clojure.core$load_one.invokeStatic || clojure.core$load_one.invoke(core.clj) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5728| clojure.core$load_lib$fn__5618.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5727| clojure.core$load_lib.invokeStatic || clojure.core$load_lib.doInvoke(core.clj) || clojure.lang.RestFn.applyTo(RestFn.java:142) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5765| clojure.core$load_libs.invokeStatic || clojure.core$load_libs.doInvoke(core.clj) || clojure.lang.RestFn.applyTo(RestFn.java:137) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|647| clojure.core$apply.invokeStatic zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|5787| clojure.core$require.invokeStatic || clojure.core$require.doInvoke(core.clj) || clojure.lang.RestFn.invoke(RestFn.java:421) || clojure.tools.analyzer.jvm.utils$eval4392.invokeStatic(form-init8663423518975891793.clj:1) || clojure.tools.analyzer.jvm.utils$eval4392.invoke(form-init8663423518975891793.clj) || clojure.lang.Compiler.eval(Compiler.java:6934) || clojure.lang.Compiler.eval(Compiler.java:6897) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|3096| clojure.core$eval.invokeStatic || clojure.core$eval.invoke(core.clj) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|240| clojure.main$repl$read_eval_print__7404$fn__7407.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|240| clojure.main$repl$read_eval_print__7404.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|258| clojure.main$repl$fn__7413.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/main.clj|258| clojure.main$repl.invokeStatic || clojure.main$repl.doInvoke(main.clj) || clojure.lang.RestFn.invoke(RestFn.java:1523) zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|58| clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn__637.invoke || clojure.lang.AFn.applyToHelper(AFn.java:152) || clojure.lang.AFn.applyTo(AFn.java:144) zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|645| clojure.core$apply.invokeStatic zipfile:/Users/michael.blume/.m2/repository/org/clojure/clojure/1.8.0-master-SNAPSHOT/clojure-1.8.0-master-SNAPSHOT.jar::clojure/core.clj|1874| clojure.core$with_bindings_STAR_.invokeStatic || clojure.core$with_bindings_STAR_.doInvoke(core.clj) || clojure.lang.RestFn.invoke(RestFn.java:425) zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|56| clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invokeStatic || clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invoke(interruptible_eval.clj) zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|191| clojure.tools.nrepl.middleware.interruptible_eval$interruptible_eval$fn__679$fn__682.invoke zipfile:/Users/michael.blume/.m2/repository/org/clojure/tools.nrepl/0.2.10/tools.nrepl-0.2.10.jar::clojure/tools/nrepl/middleware/interruptible_eval.clj|159| clojure.tools.nrepl.middleware.interruptible_eval$run_next$fn__674.invoke || clojure.lang.AFn.run(AFn.java:22) || java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) || java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) || java.lang.Thread.run(Thread.java:745)

I don't see where AOT would be involved?

0 votes
by

Comment made by: bronsa

(link: ~michaelblume) The updated patch should fix the issue you reported

0 votes
by

Comment made by: michaelblume

Cool, thanks =)

New patch no longer deletes MethodImplCache, which is not used -- is that deliberate?

0 votes
by

Comment made by: alexmiller

It would be cool if there was a bulleted list of the things changed in the patch in the description. For example: "Renamed MethodImplCache to ImplCache", etc. That helps makes it easier to review.

0 votes
by

Comment made by: bronsa

Attached is an updated patch that doesn't replace MethodImplCache with ImplCache but simply reuses MethodImplCache, reducing the impact of this patch and making it easier (and safer) to review.

0 votes
by
_Comment made by: alexmiller_

Bumping priority as this is used in new {{inst?}} predicate - see https://github.com/clojure/clojure/commit/58227c5de080110cb2ce5bc9f987d995a911b13e
0 votes
by
_Comment made by: alexmiller_

I ran the before and after tests with the v3 patch. Before times matched pretty closely but I could not replicate the after results. I got this which is actually much worse in the not found case:


(let [x (x.)] (bench (satisfies? p x))) ;; Execution time mean : 76.833504 ns
(let [y (y.)] (bench (satisfies? p y))) ;; Execution time mean : 20.570007 µs

0 votes
by
_Comment made by: bronsa_

v4 patch fixes the regression on the not-found case, not sure how that happened, apologies.
Here are the timings I'm getting now:

clojure master:

user=> (let [x (x.)] (bench (satisfies? p x)))
Evaluation count : 604961580 in 60 samples of 10082693 calls.
             Execution time mean : 112.649568 ns
    Execution time std-deviation : 12.216782 ns
   Execution time lower quantile : 99.299203 ns ( 2.5%)
   Execution time upper quantile : 144.265205 ns (97.5%)
                   Overhead used : 1.898271 ns

Found 3 outliers in 60 samples (5.0000 %)
    low-severe     2 (3.3333 %)
    low-mild     1 (1.6667 %)
 Variance from outliers : 73.7545 % Variance is severely inflated by outliers
nil




user=> (let [y (y.)] (bench (satisfies? p y)))
Evaluation count : 22676100 in 60 samples of 377935 calls.
             Execution time mean : 2.605426 µs
    Execution time std-deviation : 141.100070 ns
   Execution time lower quantile : 2.487234 µs ( 2.5%)
   Execution time upper quantile : 2.873045 µs (97.5%)
                   Overhead used : 1.898271 ns

Found 1 outliers in 60 samples (1.6667 %)
    low-severe     1 (1.6667 %)
 Variance from outliers : 40.1251 % Variance is moderately inflated by outliers
nil



master + v4:

user=> (let [x (x.)] (bench (satisfies? p x)))
Evaluation count : 731759100 in 60 samples of 12195985 calls.
             Execution time mean : 79.321426 ns
    Execution time std-deviation : 3.959245 ns
   Execution time lower quantile : 75.365187 ns ( 2.5%)
   Execution time upper quantile : 87.986479 ns (97.5%)
                   Overhead used : 1.905711 ns

Found 1 outliers in 60 samples (1.6667 %)
    low-severe     1 (1.6667 %)
 Variance from outliers : 35.2614 % Variance is moderately inflated by outliers
nil



user=> (let [y (y.)] (bench (satisfies? p y)))
Evaluation count : 771220140 in 60 samples of 12853669 calls.
             Execution time mean : 77.410858 ns
    Execution time std-deviation : 1.407926 ns
   Execution time lower quantile : 75.852530 ns ( 2.5%)
   Execution time upper quantile : 80.759226 ns (97.5%)
                   Overhead used : 1.897646 ns

Found 4 outliers in 60 samples (6.6667 %)
    low-severe     3 (5.0000 %)
    low-mild     1 (1.6667 %)
 Variance from outliers : 7.7866 % Variance is slightly inflated by outliers


So to summarize:
master found = 112ns
master not-found = 2.6us

master+v4 found = 79ns
master+v4 not-found = 77ns
0 votes
by

Comment made by: michaelblume

For records that have been declared with an implementation of a particular protocol, and which therefore implement the corresponding interface, would it make sense to use an (instance?) check against that interface as a fast path?

0 votes
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Comment made by: alexmiller

Michael - that check is already in there

Nicola - I have a few comments/questions:

  1. I don't get what the purpose of the NIL stuff is - could you explain that?
  2. In the case where x is an instance of the interface, the old code returned x and the new code in find-protocol-impl* returns interface. Why the change?
  3. This: (alter-var-root (:var protocol) assoc :impl-cache (expand-method-impl-cache cache c impl)) is not thread-safe afaict - I think simultaneous misses in two different threads for different impls would cause the cache to only have one of them. This is probably unlikely, and probably not a big deal since the cache will just be updated on the next call (not give a wrong answer), but wanted to mention it. I don't see any easy way to avoid it without a lot of changes.
0 votes
by

Comment made by: bronsa

Alex, thanks for looking at this,
1- The NIL object is a placeholder in the method impl cache for nil, as find-and-cache-protocol-impl tests for nil? to know if the dispatch has been cached or not

2- The change is purely a consistency one, making find-and-cache-protocol-impl always return a class/interface rather than either a class/interface or a concrete instance. Behaviourally, it doesn't change anything since the two consumers of find-protocol-impl, namely find-protocol-method and satisfies? don't care what that value is in that case

3- Yes you are correct that it is not thread safe, however I think it's a decent tradeoff as it doesn't cause any incorrect behaviour and at worse would cause an extra cache miss, making it thread safe would mean an extra performance penalty in every cache hit/miss

0 votes
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Comment made by: michaelblume

(link: ~bronsa) I'm seeing a change in behavior from this patch

`
(defprotocol BoolProtocol
(proto-fn [this]))

(extend-protocol BoolProtocol
Object
(proto-fn [x] "Object impl")

nil
(proto-fn [x] "Nil impl"))

(proto-fn false)
`

returns "Object impl" with Clojure master and "Nil impl" with this patch

...