Observation

Edit online

Amounts of memory and pages transferred during the relocation process.

Figure 1 shows three values sets indicating the amounts of memory transferred during various passes of the relocation process scales for different workloads, as follows:

  • The leftmost value set shows the amount of memory transferred during the first pass of the relocation process.
  • The center value set shows the average amount of memory transferred during the intermediate passes, with the number of intermediate passes indicated within circles shown above the respective columns.
  • The right value set shows the sum of the amount of memory transferred in the last two passes while the virtual system is quiesced.

For each workload, Figure 1 provides details about the number of pages transferred in various passes of the relocation process, as follows:

  • The Java™ workload (leftmost position in value sets, grey color) exhibits an amount of memory of 887 k pages (or 3548 MiB of memory) transferred in the first pass. During the intermediate passes, the average number of pages transferred stays comparatively high at about 759 k pages, and the sum of pages transferred during the final two passes (594 k pages) is again the highest value observed for the set of observed workloads. The number of intermediate passes is the lowest for the set of observed workloads.
  • The page cache file system I/O workload (second position in value sets, bright green color) exhibits the highest amount of 1019 k pages of memory transferred in the first pass of the relocation process – in other words, almost all of the virtual machine memory is transferred. During the intermediate passes, the average number of pages transferred is substantially lower (386 k pages). The sum of pages transferred during the final two passes (336 k pages) is still significant. The number of intermediate passes is just one pass more than that for the Java workload.
  • The direct I/O file system I/O workload (third position in value sets, dark green color) exhibits the lowest amount of 74 k pages (296 MiB) of memory transferred in the first pass of the relocation process, and extraordinarily low numbers of pages transferred during the intermediate (4350 pages) and final (3185 pages) passes. However, the number of intermediate passes is the same as that observed for the page cache filesystem I/O workload.
  • The transactional database workload (rightmost position in value sets, yellow color) exhibits a moderate amount of 721 k pages transferred in the first pass of the relocation process, which is about two thirds of the virtual memory. During the intermediate and final passes small amounts of pages (49 k pages and 24 k pages) are transferred. The number of intermediate passes is high, twice as much as that for the filesystem workloads.

Figure 1 shows that relocation and quiesce times for the workloads.

  • The Java workload exhibits the highest times of 22.6 s and 2.8 s.
  • The relocation time for the page cache file system I/O workload is with 18.3 s slightly shorter than that of the Java workload, and the quiesce time with 1.86 s is about 66 % of that of the Java workload.
  • The direct I/O file system I/O workload exhibits the shortest relocation time of only 3.36 s, but the quiesce time of 1.49 s is only about 20% less than that of the page cache case.
  • The transactional database workload has a relocation time of 8.65 s, and a quiesce time of 0.78 s.