Method unmap0

core/src/main/java/io/questdb/std/MmapCache.java:452–481

(long address, long len, int memoryTag)

    }

    private void unmap0(long address, long len, int memoryTag) {
        if (Files.ASYNC_MUNMAP_ENABLED) {
            // sequence returning -2 -> we lost a CAS race. we do a cheap retry
            // sequence returning -1 -> the queue is full. then it's cheaper to do the munmap ourserlves
            long seq;
            while ((seq = munmapProducesSequence.next()) == -2) {
                Os.pause();
            }

            if (seq > -1) {
                MunmapTask task = munmapTaskRingQueue.get(seq);
                task.address = address;
                task.size = len;
                task.memoryTag = memoryTag;
                munmapProducesSequence.done(seq);
                return;
            } else {
                LOG.info().$("async munmap queue is full").$();
            }
        }
        int result = Files.munmap0(address, len);
        if (result != -1) {
            Unsafe.recordMemAlloc(-len, memoryTag);
        } else {
            throw CairoException.critical(Os.errno())
                    .put("munmap failed [address=").put(address)
                    .put(", len=").put(len)
                    .put(", memoryTag=").put(memoryTag).put(']');
        }
    }

    /**
     * Cache record holding memory mapping details and reference count.