See "Avoid using virtual memory (paging to disk)." for more information. Often, swapping manifests itself as Coherence nodes being removed from the cluster due to long periods of unresponsiveness caused by them having been swapped out of RAM. Swapping can have a significant impact on Coherence's performance and should be avoided. Swapping is automatically performed by the operating system and typically occurs when the available RAM memory is depleted. Swapping, also known as paging, is the use of secondary storage to store and retrieve application data for use in RAM memory. If present, work with your system administrator to identify and correct the cause allowing the TSC timesource to be used. Kernel: Falling back to a sane timesource now.Īs the log messages suggest, this can be caused by a variable rate CPU (SpeedStep), having DMA disabled, or incorrect TSC synchronization on multi CPU computers. Kernel: Incorrect TSC synchronization on an SMP system (see dmesg). Kernel: You don't have DMA enabled for your hard disk (see hdparm), Kernel: TSC cannot be used as a timesource. It is suggested that you check your system logs ( /var/log/dmesg) to verify that the following is not present. Note that Coherence and the underlying JVM are not aware of the timesource which the operating system is using. The slower time sources can be 10 to 30 times more expensive to query then the TSC timesource, and may have a measurable impact on Coherence performance. Linux chooses TSC by default and during startup checks for inconsistencies, if found it switches to a slower safe timesource. Linux has several high resolution timesources to choose from, the fastest TSC (Time Stamp Counter) unfortunately is not always reliable.
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