Why doesnt JIT compiler ( Java ) save the results?
As I studied about JIT compiler from here:
What does a just-in-time (JIT) compiler do?
and
there's no *.exe or *.dll generated by the Java JIT for Windows. It
writes the processor instructions to memory (RAM) and runs it from
there. There's no need to create a separate PE file with file-headers
and everything
My question is WHY doesn't JIT compiler ( Java ) save the results? Isn't it useful to store compiled code to save time for the next launch?
(My question is different from the mentioned above, because I emphasized on WHY)
java jit
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
add a comment |
As I studied about JIT compiler from here:
What does a just-in-time (JIT) compiler do?
and
there's no *.exe or *.dll generated by the Java JIT for Windows. It
writes the processor instructions to memory (RAM) and runs it from
there. There's no need to create a separate PE file with file-headers
and everything
My question is WHY doesn't JIT compiler ( Java ) save the results? Isn't it useful to store compiled code to save time for the next launch?
(My question is different from the mentioned above, because I emphasized on WHY)
java jit
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
1
I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49
add a comment |
As I studied about JIT compiler from here:
What does a just-in-time (JIT) compiler do?
and
there's no *.exe or *.dll generated by the Java JIT for Windows. It
writes the processor instructions to memory (RAM) and runs it from
there. There's no need to create a separate PE file with file-headers
and everything
My question is WHY doesn't JIT compiler ( Java ) save the results? Isn't it useful to store compiled code to save time for the next launch?
(My question is different from the mentioned above, because I emphasized on WHY)
java jit
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
As I studied about JIT compiler from here:
What does a just-in-time (JIT) compiler do?
and
there's no *.exe or *.dll generated by the Java JIT for Windows. It
writes the processor instructions to memory (RAM) and runs it from
there. There's no need to create a separate PE file with file-headers
and everything
My question is WHY doesn't JIT compiler ( Java ) save the results? Isn't it useful to store compiled code to save time for the next launch?
(My question is different from the mentioned above, because I emphasized on WHY)
java jit
java jit
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
asked Jan 3 at 7:30
Axel CoonAxel Coon
458
458
1
I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49
add a comment |
1
I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49
1
1
I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49
I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49
add a comment |
1 Answer
1
active
oldest
votes
The ouput of a JIT may be different for each run - it can optimize for the current load pattern. This sometimes allows it to optimize more agressively than what would be possible for pre-compiled code that needs to be reusable.
If the load-pattern changes and the optimization is found to be sub-optimal or even adverse, a JIT can de-optimize and possibly attempt a different optimization
(see also About the dynamic de-optimization of HotSpot)
Now, it might sometimes save some performance to keep these results of various compiled versions around and reuse them later, but it would also require a significant amount of book-keeping to be able to find out if a section of code has already been compiled with currently relevant optimizations.
I suppose that is just not considered worth the effort. Its a tradeoff between doing file-IO and usually fast compilation of small sections of code.
answered Jan 3 at 7:58
HulkHulk
3,42812142
add a comment |
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1 Answer
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active
oldest
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1 Answer
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active
oldest
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oldest
votes
The ouput of a JIT may be different for each run - it can optimize for the current load pattern. This sometimes allows it to optimize more agressively than what would be possible for pre-compiled code that needs to be reusable.
If the load-pattern changes and the optimization is found to be sub-optimal or even adverse, a JIT can de-optimize and possibly attempt a different optimization
(see also About the dynamic de-optimization of HotSpot)
Now, it might sometimes save some performance to keep these results of various compiled versions around and reuse them later, but it would also require a significant amount of book-keeping to be able to find out if a section of code has already been compiled with currently relevant optimizations.
I suppose that is just not considered worth the effort. Its a tradeoff between doing file-IO and usually fast compilation of small sections of code.
answered Jan 3 at 7:58
HulkHulk
3,42812142
add a comment |
The ouput of a JIT may be different for each run - it can optimize for the current load pattern. This sometimes allows it to optimize more agressively than what would be possible for pre-compiled code that needs to be reusable.
If the load-pattern changes and the optimization is found to be sub-optimal or even adverse, a JIT can de-optimize and possibly attempt a different optimization
(see also About the dynamic de-optimization of HotSpot)
Now, it might sometimes save some performance to keep these results of various compiled versions around and reuse them later, but it would also require a significant amount of book-keeping to be able to find out if a section of code has already been compiled with currently relevant optimizations.
I suppose that is just not considered worth the effort. Its a tradeoff between doing file-IO and usually fast compilation of small sections of code.
answered Jan 3 at 7:58
HulkHulk
3,42812142
add a comment |
The ouput of a JIT may be different for each run - it can optimize for the current load pattern. This sometimes allows it to optimize more agressively than what would be possible for pre-compiled code that needs to be reusable.
If the load-pattern changes and the optimization is found to be sub-optimal or even adverse, a JIT can de-optimize and possibly attempt a different optimization
(see also About the dynamic de-optimization of HotSpot)
Now, it might sometimes save some performance to keep these results of various compiled versions around and reuse them later, but it would also require a significant amount of book-keeping to be able to find out if a section of code has already been compiled with currently relevant optimizations.
I suppose that is just not considered worth the effort. Its a tradeoff between doing file-IO and usually fast compilation of small sections of code.
answered Jan 3 at 7:58
HulkHulk
3,42812142
The ouput of a JIT may be different for each run - it can optimize for the current load pattern. This sometimes allows it to optimize more agressively than what would be possible for pre-compiled code that needs to be reusable.
If the load-pattern changes and the optimization is found to be sub-optimal or even adverse, a JIT can de-optimize and possibly attempt a different optimization
(see also About the dynamic de-optimization of HotSpot)
Now, it might sometimes save some performance to keep these results of various compiled versions around and reuse them later, but it would also require a significant amount of book-keeping to be able to find out if a section of code has already been compiled with currently relevant optimizations.
I suppose that is just not considered worth the effort. Its a tradeoff between doing file-IO and usually fast compilation of small sections of code.
answered Jan 3 at 7:58
HulkHulk
3,42812142
answered Jan 3 at 7:58
HulkHulk
3,42812142
answered Jan 3 at 7:58
HulkHulk
3,42812142
answered Jan 3 at 7:58
HulkHulk
3,42812142
3,42812142
add a comment |
add a comment |
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I don't think this is an inherently bad question, but only a developer of an actual JVM would be able to answer for certain. Most likely, it's because saving the internal JVM state would be an extremely tricky operation; that said, check into GraalVM.
– chrylis
Jan 3 at 7:49