From: Hyman Huang <yong.hu...@smartx.com> v2: 1. background sync - Throw out the idea of "not updating the bitmap" when the RAMBlock of the RAM list is iterated during migration; re-implement the background RAM dirty sync using Peter's updated method.
2. responsive throttle - Rename the "cpu-responsive throttle" to "cpu-throttle-responsive," as suggested by Fabiano. For the background sync refinement, The new method achieves a much shorter migration time overall and is much simpler than the previous approach. The test approach is the same as in version 1, but we use a new test host with 1.93 Gb bandwidth. Please refer to the information included in version 1 below for more details. The new test result for background dirty sync is as follows; we didn't test the responsive throttle feature because its logic is still the same. For each scenario, we tested twice and used 3500MB as high memory load. ramsize: 150MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 57579 | 577 | 107 | 90% | | | 57434 | 466 | 110 | 90% | |------------+-----------+----------+-----------+--------------| | background | 57728 | 488 | 102 | 90% | | sync | 60223 | 447 | 115 | 90% | |------------+-----------+----------+-----------+--------------| ramsize: 3000MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 291275 | 416 | 26 | 99% | | | 290907 | 567 | 27 | 99% | |------------+-----------+----------+-----------+--------------| | background | 210912 | 465 | 30 | 99% | | sync | 203890 | 442 | 28 | 99% | |------------+-----------+----------+-----------+--------------| ramsize: 3500MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 338445 | 491 | 28 | 99% | | | 341168 | 496 | 28 | 99% | |------------+-----------+----------+-----------+--------------| | background | 209099 | 440 | 27 | 99% | | sync | 206241 | 467 | 30 | 99% | |------------+-----------+----------+-----------+--------------| v1: This is the first version for auto-converge refinements; refer to the following link for details about the RFC version: https://patchew.org/QEMU/cover.1725891841.git.yong.hu...@smartx.com/ This series introduces two refinements called "background sync" and "responsive throttle," respectively. 1. background sync: The original auto-converge throttle logic doesn't look like it will scale because migration_trigger_throttle() is only called for each iteration, so it won't be invoked for a long time if one iteration can take a long time. The background sync would fix this issue by implementing the background dirty bitmap sync and throttle automatically once detect that the iteration lasts a long time during the migration. The background sync is implemented transparently, and there is no new-added interface for upper apps. 2. responsive throttle: The original auto-converge throttle logic determines if the migration is convergent by one criteria, and if the iteration fits twice, then launch the CPU throttle or increase the throttle percentage. This results in that the migration_trigger_throttle() won't be invoked for a long time if one iteration can take a long time too. The responsive throttle introduce one more criteria to assist detecting the convergence of the migration, if either of the two criteria is met, migration_trigger_throttle() would be called. This also makes it more likely that the CPU throttle will be activated, thereby accelerating the migration process. The responsive throttle provides the 'cpu-responsive-throttle' option to enable this feature. We test this two features with the following environment: a. Test tool: guestperf Refer to the following link to see details: https://github.com/qemu/qemu/tree/master/tests/migration/guestperf b. Test VM scale: CPU: 16; Memory: 100GB c. Average bandwidth between source and destination for migration: 1.59 Gbits/sec We use stress tool contained in the initrd-stress.img to update ramsize MB on every CPU in guest, refer to the following link to see the source code: https://github.com/qemu/qemu/blob/master/tests/migration/stress.c The following command is executed to compare our refined QEMU with the original QEMU: # python3.6 guestperf.py --binary /path/to/qemu-kvm --cpus 16 \ --mem 100 --max-iters 200 --max-time 1200 --dst-host {dst_ip} \ --kernel /path/to/vmlinuz --initrd /path/to/initrd-stress.img \ --transport tcp --downtime 500 --auto-converge --auto-converge-step 10 \ --verbose --stress-mem {ramsize} We set ramsize to 150MB to simulate the light load, 3000MB as moderate load and 5000MB as heavy load. Test cases were executed three times in each scenario. The following data shows the migration test results with an increase in stress. ramsize: 150MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 123685 | 490 | 87 | 99% | | | 116249 | 542 | 45 | 60% | | | 107772 | 587 | 8 | 0% | |------------+-----------+----------+-----------+--------------| | background | 113744 | 1654 | 16 | 20% | | sync | 122623 | 758 | 60 | 80% | | | 112668 | 547 | 23 | 20% | |------------+-----------+----------+-----------+--------------| | background | 113660 | 573 | 5 | 0% | | sync + | 109357 | 576 | 6 | 0% | | responsive | 126792 | 494 | 37 | 99% | | throttle | | | | | |------------+-----------+----------+-----------+--------------| ramsize: 3000MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 404398 | 515 | 26 | 99% | | | 392552 | 528 | 25 | 99% | | | 400113 | 447 | 24 | 99% | |------------+-----------+----------+-----------+--------------| | background | 239151 | 681 | 25 | 99% | | sync | 295047 | 587 | 41 | 99% | | | 289936 | 681 | 34 | 99% | |------------+-----------+----------+-----------+--------------| | background | 212786 | 487 | 22 | 99% | | sync + | 225246 | 666 | 23 | 99% | | responsive | 244053 | 572 | 27 | 99% | | throttle | | | | | |------------+-----------+----------+-----------+--------------| ramsize: 5000MB |------------+-----------+----------+-----------+--------------| | | totaltime | downtime | iteration | max throttle | | | (ms) | (ms) | count | percent | |------------+-----------+----------+-----------+--------------| | original | 566357 | 644 | 22 | 99% | | | 607471 | 320 | 23 | 99% | | | 603136 | 417 | 22 | 99% | |------------+-----------+----------+-----------+--------------| | background | 284605 | 793 | 27 | 99% | | sync | 272270 | 668 | 28 | 99% | | | 267543 | 545 | 28 | 99% | |------------+-----------+----------+-----------+--------------| | background | 226446 | 413 | 22 | 99% | | sync + | 232082 | 494 | 23 | 99% | | responsive | 269863 | 533 | 23 | 99% | | throttle | | | | | |------------+-----------+----------+-----------+--------------| To summarize the data above, any data that implies negative optimization does not appear, the refinement saves the total time significantly and, therefore, shortens the duration of the guest performance degradation. Additionally, we examined the memory performance curves generated from the test case results above; while no negative optimization is there, but the performance degradation occurs more quickly. Since it is inconvenient to display the graphic data, one can independently verify it. Hyman Huang (3): migration: Support background ramblock dirty sync qapi/migration: Introduce cpu-throttle-responsive parameter migration: Support responsive CPU throttle include/migration/misc.h | 3 + migration/migration-hmp-cmds.c | 8 +++ migration/migration.c | 11 +++ migration/options.c | 20 ++++++ migration/options.h | 1 + migration/ram.c | 119 ++++++++++++++++++++++++++++++++- migration/ram.h | 3 + migration/trace-events | 2 + qapi/migration.json | 16 ++++- system/cpu-timers.c | 2 + tests/qtest/migration-test.c | 30 +++++++++ 11 files changed, 212 insertions(+), 3 deletions(-) -- 2.27.0
