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From "Vladimir Ozerov (JIRA)" <j...@apache.org>
Subject [jira] [Created] (IGNITE-1615) .Net: Perform AtomicLong.get() without JNI if possible.
Date Mon, 05 Oct 2015 07:59:26 GMT
Vladimir Ozerov created IGNITE-1615:
---------------------------------------

             Summary: .Net: Perform AtomicLong.get() without JNI if possible.
                 Key: IGNITE-1615
                 URL: https://issues.apache.org/jira/browse/IGNITE-1615
             Project: Ignite
          Issue Type: Task
          Components: interop
    Affects Versions: ignite-1.4
            Reporter: Vladimir Ozerov
             Fix For: ignite-1.5


Variables with atomic/interlocked semantics are frequently used in mostly-read scenarios.
E.g. in spin-loops, non-blocking alogrithms, as regular volatiles, etc..

With current implementation we perform JNI call on every read which is too expensive, especially
with poor Java performance when performing (native -> JVM) transition.

We can optimize it with the following non-blocking algorithm:
1) Add atomic "stamp" field.
2) Add atomic "cached" field.
3) On any update:
- Do the update;
- Atomically increment the stamp;
4) On any read:
- Read stamp (oldStamp);
- Read cached value;
- Read stamp again (newStamp);
- if (oldStamp == newStamp == cache.stamp()), return cached value.
- Otherwise perform real read through JNI and update cached value with a pair of (readValue
+ oldStamp);



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