shubhamsrkdev commented on code in PR #15585:
URL: https://github.com/apache/lucene/pull/15585#discussion_r2721591904
##########
lucene/core/src/java/org/apache/lucene/store/MemorySegmentIndexInput.java:
##########
@@ -74,12 +75,28 @@ public static MemorySegmentIndexInput newInstance(
boolean confined,
Function<IOContext, ReadAdvice> toReadAdvice) {
assert
Arrays.stream(segments).map(MemorySegment::scope).allMatch(arena.scope()::equals);
+ AtomicInteger sharedPrefetchCounter = new AtomicInteger();
Review Comment:
>Is this creating one AtomicInteger per actually originally opened files?
And then each clone shares that same original AtomicInteger?
Yes!
>Hmm what happens when we overflow the int? What does incrementAndGet do
then? Silently overflow/wraparound to negative?
It does wraparound after `Integer.MAX_VALUE` to `Integer.MIN_VALUE` and
subsequent negative values. But it would just cause an extra prefetch because
of `isZeroOrPowerOfTwo` ?`isZeroOrPowerOfTwo(Integer.MIN_VALUE)` would give
true but subsequent increments would just give false as expected. For example:
```
import java.util.concurrent.atomic.AtomicInteger;
class Main {
public static void main(String[] args) {
AtomicInteger counter = new AtomicInteger(Integer.MAX_VALUE);
while(counter.incrementAndGet() < 0)
{
System.out.println(isZeroOrPowerOfTwo(counter.get()));
}
}
public static boolean isZeroOrPowerOfTwo(int x) {
return (x & (x - 1)) == 0;
}
}
```
This would give:
```
true
false
false
false
false
false
false
false
false
false
false
.
.
.
.
.
.
.
.
.
```
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