Is it reasonable to compare outputs between JMH and hprof?
Xuelei Fan
xuelei.fan at oracle.com
Thu Dec 4 12:40:24 UTC 2014
On 12/4/2014 8:20 PM, Weijun Wang wrote:
>
>
> On 12/4/2014 19:57, Xuelei Fan wrote:
>>> These are calls with SHA (i.e. SHA1) or SHA2 in the stack
>>> (depth=4), and time for SHA2 vs SHA1 is 45.38% vs 1.09%.
>>
>> Where is the other 98.91% cost for SHA1? You only call message digest
>> in the test, instinctively, shall most of the resources are cost by the
>> message digest, directly or indirectly?
>
> The program call SHA2 and SHA1, they together spend 46% of time.
>
Oh, I see.
> The other 54% is spent on file reading, unzip, char/string manipulation
> etc.
>
Hm, should some of the 54% be actually counted for SHA-1? Maybe you can
dump more stack depth, and look at whether car/string/etc manipulation
are actually called by SHA-1.
Xuelei
> --Max
>
>>
>> Xuelei
>>
>>
>> On 12/4/2014 12:09 PM, Wang Weijun wrote:
>>> Hi All
>>>
>>> I am comparing the difference of SHA-1 and SHA-256. First I wrote a
>>> JMH benchmark:
>>>
>>> @Benchmark
>>> public void sig1(Blackhole bh) throws Exception {
>>> bh.consume(sig("SHA-1"));
>>> }
>>>
>>> @Benchmark
>>> public void sig2(Blackhole bh) throws Exception {
>>> bh.consume(sig("SHA-256"));
>>> }
>>>
>>> byte[] sig(String alg) throws Exception {
>>> MessageDigest md = MessageDigest.getInstance(alg);
>>> md.update(new byte[10000]);
>>> return md.digest();
>>> }
>>>
>>> The output is
>>>
>>> Benchmark Mode Samples Score Error Units
>>> o.o.b.Weird.sig1 thrpt 5 20984.435 ± 3356.455 ops/s
>>> o.o.b.Weird.sig2 thrpt 5 13130.330 ± 976.824 ops/s
>>>
>>> so the difference is there but not huge.
>>>
>>> Then I wrote a simple app with
>>>
>>> public static void main(String args[]) throws Exception {
>>> int i = Arrays.hashCode(sig("SHA-1"));
>>> i += Arrays.hashCode(sig("SHA-256"));
>>> System.out.println(i);
>>> }
>>>
>>> static byte[] sig(String alg) throws Exception {
>>> MessageDigest md = MessageDigest.getInstance(alg);
>>> md.update(new byte[10000]);
>>> return md.digest();
>>> }
>>>
>>> and then profile it with -agentlib:hprof=cpu=times, and get
>>>
>>> SHA2 1 10.16% 10.16% 156 303276
>>> sun.security.provider.SHA2.implCompress
>>> SHA2 2 6.91% 17.07% 9984 303274
>>> sun.security.provider.SHA2.lf_sigma0
>>> SHA2 3 5.28% 22.36% 9984 303271
>>> sun.security.provider.SHA2.lf_sigma1
>>> SHA2 4 4.61% 26.96% 7488 303269
>>> sun.security.provider.SHA2.lf_delta0
>>> SHA2 5 4.20% 31.17% 29952 303273 sun.security.provider.SHA2.lf_S
>>> SHA2 7 3.79% 39.16% 7488 303266
>>> sun.security.provider.SHA2.lf_delta1
>>> SHA2 9 2.85% 44.99% 29952 303270 sun.security.provider.SHA2.lf_S
>>> SHA2 13 1.90% 54.47% 14976 303267 sun.security.provider.SHA2.lf_S
>>> SHA2 17 1.49% 61.25% 14976 303264 sun.security.provider.SHA2.lf_S
>>> SHA2 22 0.81% 66.12% 7488 303265 sun.security.provider.SHA2.lf_R
>>> SHA2 23 0.81% 66.94% 9984 303275 sun.security.provider.SHA2.lf_maj
>>> SHA2 25 0.81% 68.56% 156 303263
>>> sun.security.provider.ByteArrayAccess.b2iBig64
>>> SHA2 27 0.68% 70.05% 9984 303272 sun.security.provider.SHA2.lf_ch
>>> SHA2 31 0.54% 72.63% 7488 303268 sun.security.provider.SHA2.lf_R
>>> SHA1 34 0.54% 74.25% 156 303224
>>> sun.security.provider.SHA.implCompress
>>> SHA1 43 0.41% 78.05% 156 303223
>>> sun.security.provider.ByteArrayAccess.b2iBig64
>>> SHA2 60 0.27% 82.66% 2496 303262 java.lang.Integer.reverseBytes
>>> SHA2 61 0.27% 82.93% 64 303290
>>> sun.security.provider.SHA2.lf_sigma1
>>> SHA1 116 0.14% 91.06% 2496 303222 java.lang.Integer.reverseBytes
>>>
>>> These are calls with SHA (i.e. SHA1) or SHA2 in the stack (depth=4),
>>> and time for SHA2 vs SHA1 is 45.38% vs 1.09%. With such a small app I
>>> don't think SHA or SHA2 is called anywhere else. This is jdk9 b40.
>>>
>>> Why is the output so different from JMH? Is it reasonable comparing
>>> them?
>>>
>>> Thanks
>>> Max
>>>
>>
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