RFR: 8259065: Optimize MessageDigest.getInstance [v4]

[Valerie Peng]

On Thu, 7 Jan 2021 03:59:13 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> By caching default constructors used in `java.security.Provider::newInstanceUtil` in a `ClassValue`, we can reduce the overhead of allocating instances in a variety of places, e.g., `MessageDigest::getInstance`, without compromising thread-safety or security.
>> 
>> On the provided microbenchmark `MessageDigest.getInstance(digesterName)` improves substantially for any `digesterName` - around -90ns/op and -120B/op:
>> Benchmark                                                                  (digesterName)  Mode  Cnt     Score     Error   Units
>> GetMessageDigest.getInstance                                                          md5  avgt   30   293.929 ±  11.294   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                      md5  avgt   30   424.028 ±   0.003    B/op
>> GetMessageDigest.getInstance                                                        SHA-1  avgt   30   322.928 ±  16.503   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                    SHA-1  avgt   30   688.039 ±   0.003    B/op
>> GetMessageDigest.getInstance                                                      SHA-256  avgt   30   338.140 ±  13.902   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                  SHA-256  avgt   30   640.037 ±   0.002    B/op
>> GetMessageDigest.getInstanceWithProvider                                              md5  avgt   30   312.066 ±  12.805   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                          md5  avgt   30   424.029 ±   0.003    B/op
>> GetMessageDigest.getInstanceWithProvider                                            SHA-1  avgt   30   345.777 ±  16.669   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                        SHA-1  avgt   30   688.040 ±   0.003    B/op
>> GetMessageDigest.getInstanceWithProvider                                          SHA-256  avgt   30   371.134 ±  18.485   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                      SHA-256  avgt   30   640.039 ±   0.004    B/op
>> Patch:
>> Benchmark                                                                  (digesterName)  Mode  Cnt     Score     Error   Units
>> GetMessageDigest.getInstance                                                          md5  avgt   30   210.629 ±   6.598   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                      md5  avgt   30   304.021 ±   0.002    B/op
>> GetMessageDigest.getInstance                                                        SHA-1  avgt   30   229.161 ±   8.158   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                    SHA-1  avgt   30   568.030 ±   0.002    B/op
>> GetMessageDigest.getInstance                                                      SHA-256  avgt   30   260.013 ±  15.032   ns/op
>> GetMessageDigest.getInstance:·gc.alloc.rate.norm                                  SHA-256  avgt   30   520.030 ±   0.002    B/op
>> GetMessageDigest.getInstanceWithProvider                                              md5  avgt   30   231.928 ±  10.455   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                          md5  avgt   30   304.020 ±   0.002    B/op
>> GetMessageDigest.getInstanceWithProvider                                            SHA-1  avgt   30   247.178 ±  11.209   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                        SHA-1  avgt   30   568.029 ±   0.002    B/op
>> GetMessageDigest.getInstanceWithProvider                                          SHA-256  avgt   30   265.625 ±  10.465   ns/op
>> GetMessageDigest.getInstanceWithProvider:·gc.alloc.rate.norm                      SHA-256  avgt   30   520.030 ±   0.003    B/op
>> 
>> See: https://cl4es.github.io/2021/01/04/Investigating-MD5-Overheads.html#reflection-overheads for context.
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address review comments from @valeriep

src/java.base/share/classes/java/security/Provider.java line 1072:

> 1070:         }
> 1071:         public int hashCode() {
> 1072:             return 31*31 + type.hashCode()*31 + algorithm.hashCode();

Well, perhaps we just revert to Objects.hash(...) (better readability and potential future enhancement in case one is available)? Or, if we want to adopt the same calculation based on current Objects.hash(..) impl, the 31*31 part doesn't not seem to be too useful and can be removed for this particular case.

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PR: https://git.openjdk.java.net/jdk/pull/1933