On Wed, 17 Nov 2021 18:48:14 GMT, Volker Simonis <simo...@openjdk.org> wrote:
> In JDK 9, function objects implemented as anonymous inner classes in > java.util.regex.Pattern have been replaced by lambda functions (see > [JDK-8151481](https://bugs.openjdk.java.net/browse/JDK-8151481)). This led to > a significant performance regression (up to ~8X) for patterns with negated > character classes (e.g. "[^A-Za-z0-9]"). > > JDK 8 > ----- > Benchmark (patternString) > (text) Mode Cnt Score Error Units > FindPattern.testFind [^A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 241.359 ± 142.079 > ns/op > FindPattern.testFind [^A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 754.492 ± 181.505 > ns/op > FindPattern.testFind [A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 738.998 ± 402.188 > ns/op > FindPattern.testFind [A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 260.550 ± 118.717 > ns/op > > JDK 17 > ------ > Benchmark (patternString) > (text) Mode Cnt Score Error Units > FindPattern.testFind [^A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 1921.954 ± 90.698 > ns/op > FindPattern.testFind [^A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 2496.115 ± 555.147 > ns/op > FindPattern.testFind [A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 873.154 ± 178.640 > ns/op > FindPattern.testFind [A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 349.939 ± 33.585 > ns/op > > JDK 17 fixed > ------------------- > Benchmark (patternString) > (text) Mode Cnt Score Error Units > FindPattern.testFind [^A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 343.541 ± 181.147 > ns/op > FindPattern.testFind [^A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 744.226 ± 114.802 > ns/op > FindPattern.testFind [A-Za-z0-9] > abcdefghijklmnop1234567890ABCDEFGHIJKLMNOP avgt 3 753.297 ± 216.331 > ns/op > FindPattern.testFind [A-Za-z0-9] > ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, avgt 3 240.142 ± 13.339 > ns/op > > > ## TL;DR > > The reason for this regression is trashing of the `_secondary_super_cache` > entry in the generated Lambda classes. During matching we alternately call > methods from different interfaces on the generated Lambda class objects with > the effect that the quick type check against the `_secondary_super_cache` > continuously fails. Consequently we have to take the slow path which does a > linear search over all secondary super types and updates > `_secondary_super_cache`. > > This was the "short" description but as I've personally found the details > quite intricate I've wrote a much more detailed description of the problem at > the end of this PR. > > The fix of the problem is quite simple. Move the Lambda-generating methods > out of the function interfaces. As a result the calls to the lambda functions > become static and don't depend on the exact type of the Lambda classes any > more. > > I've also removed the overloaded `union(CharPredicate... predicates)` version > from `BmpCharPredicate`. First, it is not used anywhere anyway but second and > more important, its implementation is plain wrong. You can't cast a > `CharPredicate` into a `BmpCharPredicate` - this will deterministically lead > to a `ClassCastException` at runtime. That said, I think I understand the > motivation behind that overloaded version of `union(..)`. It could be use to > minimize the number of union nodes (i.e. predicates) for character classes > with more than two ranges (e.g. [a-zA-Z0-9]). But I leave that optimization > and a correct implementation of `union(CharPredicate... predicates)` for a > future change. > > ## Long, but maybe worth reading :) > > Currently, when a `Pattern` is compiled, we build a tree of `Pattern$Node`s. > Each `Node` has a `match()` method to match its part of the pattern. For > matching a character we use the general `CharProperty` node and the derived > `BmpCharProperty` node which only match characters from the [Basic > Multilingual > Plane](https://en.wikipedia.org/wiki/Plane_(Unicode)#Basic_Multilingual_Plane) > (i.e. characters which can be encoded in 16 bits). These nodes take a > `CharPredicate` or `BmpCharPredicate` argument respectively which are used to > decide if the character in question will be matched. `BmpCharPredicate` is a > specialization of and derived from `CharPredicate`. Since JDK 9 > `CharPredicate`/`BmpCharPredicate` are `@FunctionalInterface`s which are > implemented by various Lambda functions. They all implement the `boolean > CharPredicate::is(int ch)` function which decides if a given character > matches. `CharPredicate`s can be combined to a tree to match more complex > character classes. > > In order to match a character class like "[^A-Za-z0-9]" the corresponding > compiled `Pattern` will contain a `CharProperty` node with the following > `CharPredicate` tree: > > > Negate > | > | > | > Union > |\ > | \ > | ___________________________________________ > | | > | | > Union Range (0-9) > |\ > | \ > | ___________________________________________ > | | > | | > Range (A-Z) Range (a-z) > > > Every node in this tree implements `CharPredicate` or `BmpCharPredicate`. > They are currently all implemented as Lambda functions (see > [Pattern.java](https://github.com/openjdk/jdk/blob/e5ffdf9120c14b38e4c8794888d2002e2686ebfc/src/java.base/share/classes/java/util/regex/Pattern.java#L5608)): > > > @FunctionalInterface > static interface CharPredicate { > boolean is(int ch); > > default CharPredicate union(CharPredicate p) { > return ch -> is(ch) || p.is(ch); > } > default CharPredicate negate() { > return ch -> !is(ch); > } > ... > } > static interface BmpCharPredicate extends CharPredicate { > default CharPredicate union(CharPredicate p) { > if (p instanceof BmpCharPredicate) > return (BmpCharPredicate)(ch -> is(ch) || p.is(ch)); > return ch -> is(ch) || p.is(ch); > } > ... > } > static CharPredicate Range(int lower, int upper) { > if (upper < Character.MIN_HIGH_SURROGATE || > lower > Character.MAX_LOW_SURROGATE && > upper < Character.MIN_SUPPLEMENTARY_CODE_POINT) > return (BmpCharPredicate)(ch -> inRange(lower, ch, upper)); > return ch -> inRange(lower, ch, upper); > } > > > `Range` is a Lambda function which captures a `lower` and an `upper` bound > and calls `isRange()` for a given character to check if this character falls > inside the predefined range. A `Union` captures two existing `CharPredicate`s > and evaluates if at least one of them is true for a given character. > > Because `Range(int lower, int upper){..}` is a static method of the `Pattern` > class, the Lambda it returns will trigger the generation of a synthetic > Lambda class (i.e. `Pattern$$Lambda$20`) which implements `CharPredicate` or > `BmpCharPredicate` (depending on `lower`/`upper`) and calls a synthetic > Lambda method (i.e. `Pattern::lambda$Range$10()`) which will be injected into > the `Pattern` class. > > For `Union`/`Negate` things are a little more complicated. These Lambdas are > generated from default methods in the `CharPredicate`/`BmpCharPredicate` > interfaces. So for a `Union` of two `BmpCharPredicate`s > `BmpCharPredicate::union()` will generate a synthetic Lambda class (i.e. > `Pattern$BmpCharPredicate$$Lambda$21`) which calls a Lambda method (i.e. > `Pattern$BmpCharPredicate::lambda$union$2()`) which will be injected into the > `BmpCharPredicate` interface. > > The `Negate` and `Union` Lambda class also capture one respectively two > `CharPredicate`/`BmpCharPredicate` objects. I.e. for `Negate` it's the > implicit `this` parameter which is always a `CharPredicate`, for `Union` it's > the implicit `this` parameter which is either a `CharPredicate` or a > `BmpCharPredicate` object (depending on which overloaded version of `union()` > we call) and the additional `CharPredicate` object which is passed in as a > parameter. > > With this information we can refine our previously depicted predicate tree as > follows: > > > Negate > (CharPredicate$$Lambda$22) > | > | > | > Union > (BmpCharPredicate$$Lambda$21) > |\ > | \ > | ___________________________________________ > | | > | | > Union Range 0-9 > (BmpCharPredicate$$Lambda$21) (Pattern$$Lambda$20) > |\ > | \ > | ___________________________________________ > | | > | | > Range A-Z Range a-z > (Pattern$$Lambda$20) (Pattern$$Lambda$20) > > > When we start to match the first character with this pattern, we'll arrive at > the following stack trace: > > > [1] java.util.regex.Pattern.inRange (Pattern.java:5,728) > [2] java.util.regex.Pattern.lambda$Range$10 (Pattern.java:5,738) > [3] java.util.regex.Pattern$$Lambda$20/0x0000000080001c60.is (null) > [4] java.util.regex.Pattern$BmpCharPredicate.lambda$union$2 > (Pattern.java:5,636) > [5] > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x0000000080080000.is > (null) > [6] java.util.regex.Pattern$BmpCharPredicate.lambda$union$2 > (Pattern.java:5,636) > [7] > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x0000000080080000.is > (null) > [8] java.util.regex.Pattern$CharPredicate.lambda$negate$3 > (Pattern.java:5,623) > [9] java.util.regex.Pattern$CharPredicate$$Lambda$22/0x0000000080080278.is > (null) > [10] java.util.regex.Pattern$CharProperty.match (Pattern.java:3,940) > [11] java.util.regex.Pattern$StartS.match (Pattern.java:3,651) > [12] java.util.regex.Matcher.search (Matcher.java:1,728) > [13] java.util.regex.Matcher.find (Matcher.java:745) > > > We first call `is()` on a `Negate` node which is actually a > `CharPredicate$$Lambda$22` (frame [9] in the stack trace): > > final class java.util.regex.Pattern$CharPredicate$$Lambda$22 implements > java.util.regex.Pattern$CharPredicate { > private final java.util.regex.Pattern$CharPredicate arg$1; > public boolean is(int) { > 0: aload_0 > 1: getfield #15 // Field > arg$1:Ljava/util/regex/Pattern$CharPredicate; > 4: iload_1 > 5: invokeinterface #20, 2 // InterfaceMethod > java/util/regex/Pattern$CharPredicate.lambda$negate$3:(I)Z > 10: ireturn > > > When the `Negate` predicate was created it captured another predicate, a > `Union` predicate of exact type `BmpCharPredicate$$Lambda$21` in this case, > and stored it in its private `arg$1` field. Next > `java.util.regex.Pattern$CharPredicate::lambda$negate$3` will be called on > this `BmpCharPredicate$$Lambda$21` object. `lambda$negate$3` is a synthetic > method which was injected into the `java.util.regex.Pattern$CharPredicate` > interface. The JVM will check for this call that `arg$1` implements > `Pattern$CharPredicate`. `arg$1` is actually of type > `BmpCharPredicate$$Lambda$21` but `BmpCharPredicate$$Lambda$21` has > `Pattern$CharPredicate` as one of its "secondary subtypes". The JVM will > detect this and will **store `Pattern$CharPredicate` in the > `_secondary_super_cache` field of `BmpCharPredicate$$Lambda$21`'s instance > klass** for quicker lookup in the future. Finally, `lambda$negate$3` itself > calls `is()` on itself and returns the negated result of that call: > > > private boolean Pattern$CharPredicate::lambda$negate$3(int) { > 0: aload_0 > 1: iload_1 > 2: invokeinterface #12, 2 // InterfaceMethod > java/util/regex/Pattern$CharPredicate.is:(I)Z > 7: ifne 14 > 10: iconst_1 > 11: goto 15 > 14: iconst_0 > 15: ireturn > > > Now remember that the current predicate object on which we've invoked > `lambda$negate$3` is really a `Union` predicate (i.e. an instance of > `BmpCharPredicate$$Lambda$21`) which overrides `is()` so we will be actually > calling `BmpCharPredicate$$Lambda$21::is()` (frame [7] in the stack trace): > > final class java.util.regex.Pattern$BmpCharPredicate$$Lambda$21 implements > java.util.regex.Pattern$BmpCharPredicate { > private final java.util.regex.Pattern$BmpCharPredicate arg$1; > private final java.util.regex.Pattern$CharPredicate arg$2; > public boolean is(int) { > 0: aload_0 > 1: getfield #17 // Field > arg$1:Ljava/util/regex/Pattern$BmpCharPredicate; > 4: aload_0 > 5: getfield #19 // Field > arg$2:Ljava/util/regex/Pattern$CharPredicate; > 8: iload_1 > 9: invokeinterface #25, 3 // InterfaceMethod > java/util/regex/Pattern$BmpCharPredicate.lambda$union$2:(Ljava/util/regex/Pattern$CharPredicate;I)Z > 14: ireturn > > > When the `Pattern$BmpCharPredicate$$Lambda$21` predicate was created it > captured two other predicates in its private `arg$1` and `arg$2` fields. On > the first one in `arg$1`, `BmpCharPredicate$$Lambda$21::is()` will now invoke > the `Pattern$BmpCharPredicate::lambda$union$2(..)` method (frame [6]). > Because this lambda method was created from the > `Pattern$BmpCharPredicate::union(..)` default method, it was injected into > the `Pattern$BmpCharPredicate` class. Therefore the JVM will now have to make > sure that `arg$1`'s class implements `Pattern$BmpCharPredicate`. > Unfortunately, the `_secondary_super_cache` field of > `BmpCharPredicate$$Lambda$21`'s instance klass is currently containing the > `Pattern$CharPredicate` interface. So we'll have to take the slow path again > and search all of `BmpCharPredicate$$Lambda$21` secondary supertypes. At the > end of this search we will find **`Pattern$BmpCharPredicate` as an > implemented supertype and store it in the `_secondary_super_cache` field of > `BmpChar Predicate$$Lambda$21`'s instance klass** (overwriting the previous `Pattern$CharPredicate` value). > > `BmpCharPredicate$$Lambda$21`'s secondary supertype cached in the > `_secondary_super_cache` field will now constantly bounce between > `Pattern$BmpCharPredicate` and `Pattern$CharPredicate` forcing every check to > go through the slow path and updating the field. This is the major reason of > the performance regression observed for patterns with negated character > classes like "[^A-Za-z0-9]". It can be clearly seen in a JMH profile: > > > ....[Hottest > Regions]............................................................................... > 24.72% c2, level 4 > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21.0x00000007c0149fc8::is, > version 609 (138 bytes) > 19.95% c2, level 4 > java.util.regex.Pattern$CharPredicate$$Lambda$22.0x00000007c014a240::is, > version 621 (102 bytes) > > ....[Hottest Region > 1].............................................................................. > c2, level 4, > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21.0x00000007c0149fc8::is, > version 609 (138 bytes) > 0.48% 0x00007fffe0482fcf: mov 0x10(%rsi),%r11d > ;*getfield arg$2 {reexecute=0 rethrow=0 return_oop=0} > ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@5 > 0.08% 0x00007fffe0482fd3: mov 0xc(%rsi),%r10d > ;*getfield arg$1 {reexecute=0 rethrow=0 return_oop=0} > ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@1 > 0x00007fffe0482fd7: nopw 0x0(%rax,%rax,1) > 0.26% 0x00007fffe0482fe0: mov 0x8(%r12,%r10,8),%ecx ; > implicit exception: dispatches to 0x00007fffe0483071 > 0.37% 0x00007fffe0482fe5: movabs $0x7c01498f8,%rax ; > {metadata('java/util/regex/Pattern$BmpCharPredicate')} > 0.04% 0x00007fffe0482fef: xor %rsi,%rsi > 0.03% 0x00007fffe0482ff2: lea (%rsi,%rcx,8),%rsi > 1.77% 0x00007fffe0482ff6: mov 0x20(%rsi),%r9 > 0.01% 0x00007fffe0482ffa: nopw 0x0(%rax,%rax,1) > 0.29% 0x00007fffe0483000: cmp %rax,%r9 > 0.26% ╭ 0x00007fffe0483003: jne 0x00007fffe048302b > ;*invokeinterface lambda$union$2 {reexecute=0 rethrow=0 return_oop=0} > │ ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@9 > │ ↗ 0x00007fffe0483005: lea (%r12,%r10,8),%rsi > ;*getfield arg$1 {reexecute=0 rethrow=0 return_oop=0} > │ │ ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@1 > │ │ 0x00007fffe0483009: mov %r11,%rdx > 0.36% │ │ 0x00007fffe048300c: shl $0x3,%rdx > ;*getfield arg$2 {reexecute=0 rethrow=0 return_oop=0} > │ │ ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@5 > 0.27% │ │ 0x00007fffe0483010: mov %r8d,%ecx > 0.41% │ │ 0x00007fffe0483013: callq 0x00007fffd8fa6700 ; > ImmutableOopMap {} > │ │ > ;*invokeinterface lambda$union$2 {reexecute=0 rethrow=0 return_oop=0} > │ │ ; - > java.util.regex.Pattern$BmpCharPredicate$$Lambda$21/0x00000007c0149fc8::is@9 > │ │ ; > {optimized virtual_call} > 0.59% │ │ 0x00007fffe0483018: add $0x20,%rsp > 0.01% │ │ 0x00007fffe048301c: pop %rbp > 0.50% │ │ 0x00007fffe048301d: cmp 0x338(%r15),%rsp ; > {poll_return} > │ │ 0x00007fffe0483024: ja 0x00007fffe0483084 > 0.10% │ │ 0x00007fffe048302a: retq > ↘ │ 0x00007fffe048302b: push %rax > │ 0x00007fffe048302c: mov %rax,%rax > │ 0x00007fffe048302f: mov 0x28(%rsi),%rdi > 0.89% │ 0x00007fffe0483033: mov (%rdi),%ecx > │ 0x00007fffe0483035: add $0x8,%rdi > │ 0x00007fffe0483039: test %rax,%rax > 8.19% │ 0x00007fffe048303c: repnz scas %es:(%rdi),%rax > 7.41% │ 0x00007fffe048303f: pop %rax > ╭│ 0x00007fffe0483040: jne 0x00007fffe048304a > 0.69% ││ 0x00007fffe0483046: mov %rax,0x20(%rsi) > 0.00% ↘╰ 0x00007fffe048304a: je 0x00007fffe0483005 > > ....[Hottest Region > 2].............................................................................. > c2, level 4, > java.util.regex.Pattern$CharPredicate$$Lambda$22.0x00000007c014a240::is, > version 621 (102 bytes) > 0.17% 0x00007fffe04897c8: sub $0x20,%rsp > ;*synchronization entry > ; - > java.util.regex.Pattern$CharPredicate$$Lambda$22/0x00000007c014a240::is@-1 > 0.01% 0x00007fffe04897cc: mov 0xc(%rsi),%r11d > ;*getfield arg$1 {reexecute=0 rethrow=0 return_oop=0} > ; - > java.util.regex.Pattern$CharPredicate$$Lambda$22/0x00000007c014a240::is@1 > 0.37% 0x00007fffe04897d0: mov 0x8(%r12,%r11,8),%r10d ; > implicit exception: dispatches to 0x00007fffe0489849 > 0.00% 0x00007fffe04897d5: movabs $0x7c0149710,%rax ; > {metadata('java/util/regex/Pattern$CharPredicate')} > 0.12% 0x00007fffe04897df: xor %rsi,%rsi > 0.16% 0x00007fffe04897e2: lea (%rsi,%r10,8),%rsi > 1.07% 0x00007fffe04897e6: mov 0x20(%rsi),%r10 > 0.00% 0x00007fffe04897ea: cmp %rax,%r10 > 0.34% ╭ 0x00007fffe04897ed: jne 0x00007fffe048980b > ;*invokeinterface lambda$negate$3 {reexecute=0 rethrow=0 return_oop=0} > │ ; - > java.util.regex.Pattern$CharPredicate$$Lambda$22/0x00000007c014a240::is@5 > │ ↗ 0x00007fffe04897ef: lea (%r12,%r11,8),%rsi > 0.31% │ │ 0x00007fffe04897f3: callq 0x00007fffd8fa93e0 ; > ImmutableOopMap {} > │ │ > ;*invokeinterface lambda$negate$3 {reexecute=0 rethrow=0 return_oop=0} > │ │ ; - > java.util.regex.Pattern$CharPredicate$$Lambda$22/0x00000007c014a240::is@5 > │ │ ; > {optimized virtual_call} > │ │ 0x00007fffe04897f8: add $0x20,%rsp > 0.25% │ │ 0x00007fffe04897fc: pop %rbp > 0.00% │ │ 0x00007fffe04897fd: cmp 0x338(%r15),%rsp ; > {poll_return} > │ │ 0x00007fffe0489804: ja 0x00007fffe0489858 > 0.03% │ │ 0x00007fffe048980a: retq > ↘ │ 0x00007fffe048980b: push %rax > 0.00% │ 0x00007fffe048980c: mov %rax,%rax > │ 0x00007fffe048980f: mov 0x28(%rsi),%rdi > 0.91% │ 0x00007fffe0489813: mov (%rdi),%ecx > 0.00% │ 0x00007fffe0489815: add $0x8,%rdi > │ 0x00007fffe0489819: test %rax,%rax > 7.59% │ 0x00007fffe048981c: repnz scas %es:(%rdi),%rax > 7.68% │ 0x00007fffe048981f: pop %rax > ╭│ 0x00007fffe0489820: jne 0x00007fffe048982a > 0.65% ││ 0x00007fffe0489826: mov %rax,0x20(%rsi) > ↘╰ 0x00007fffe048982a: je 0x00007fffe04897ef > > > There might be ways to handle such situations more intelligently in the > `LambdaMetafactory` when creating the lambda classes or in HotSpot when doing > the type checks for a call. But this must be left for a future enhancement. > For now I propose to fix this right in the Java code of `Pattern.java`. > There's no reason to create the lambda functions right in the default methods > of the functional interfaces. We can just as well move the lambda creation > into static helper functions in the `Pattern` class. This way the lambda > helper functions like `lambda$negate$3` and `lambda$union$2` can be invoked > with an `invokestatic` bytecode on the `Patter` class and avoid the secondary > subtype checks which caused the problems in the original implementation. > > Notice that the current `invokeinterface` calls in the Lambda classes `is()` > methods where only introduced in JDK 15 with [JDK-8238358: Implementation of > JEP 371: Hidden Classes](https://bugs.openjdk.java.net/browse/JDK-8238358). > Before that (e.g. in JDK 11), `LambdaMetafactory` created `invokespecial` > calls to the `lambda$negate$3`/`lambda$union$2` lambda methods. With regards > to this issue, that makes no difference because the JVM does the same > secondary sub-type checking for both `invokespecial` and `invokeinterface`. > However, [JDK-8238358](https://bugs.openjdk.java.net/browse/JDK-8238358) has > introduced another regression in C1's [interface > call](https://wiki.openjdk.java.net/display/HotSpot/InterfaceCalls) > implementation which is currently tracked under [JDK-8274983: Pattern.matcher > performance regression after > JDK-8238358](https://bugs.openjdk.java.net/browse/JDK-8274983). These changes > will workaround that regressions described in > [JDK-8274983](https://bugs.openjdk.java.net/ browse/JDK-8274983) for some patterns but can obviously not solve the C1 weakness in general. Hi Volker, good finding and a sensible way to fix the performance regression, given that the type checking mechanism in hotspot is as it is. ------------- Marked as reviewed by clanger (Reviewer). PR: https://git.openjdk.java.net/jdk/pull/6434
