From: Hyman Huang(黄勇) <huang...@chinatelecom.cn> this patchset introduce a mechanism to impose dirty restraint on vCPU, aiming to keep the vCPU running in a certain dirtyrate given by user. dirty restraint on vCPU maybe an alternative method to implement convergence logic for live migration, which could improve guest memory performance during migration compared with traditional method in theory.
For the current live migration implementation, the convergence logic throttles all vCPUs of the VM, which has some side effects. -'read processes' on vCPU will be unnecessarily penalized - throttle increase percentage step by step, which seems struggling to find the optimal throttle percentage when dirtyrate is high. - hard to predict the remaining time of migration if the throttling percentage reachs 99% to a certain extent, the dirty restraint machnism can fix these effects by throttling at vCPU granularity during migration. the implementation is rather straightforward, we calculate vCPU dirtyrate via the Dirty Ring mechanism periodically as the commit 0e21bf246 "implement dirty-ring dirtyrate calculation" does, for vCPU that be specified to impose dirty restraint, we throttle it periodically as the auto-converge does, once after throttling, we compare the quota dirtyrate with current dirtyrate, if current dirtyrate is not under the quota, increase the throttling percentage until current dirtyrate is under the quota. this patchset is the basis of implmenting a new auto-converge method for live migration, we introduce two qmp commands for impose/cancel the dirty restraint on specified vCPU, so it also can be an independent api to supply the upper app such as libvirt, which can use it to implement the convergence logic during live migration, supplemented with the qmp 'calc-dirty-rate' command or whatever. we post this patchset for RFC and any corrections and suggetions about the implementation, api, throttleing algorithm or whatever are very appreciated! Please review, thanks ! Best Regards ! Hyman Huang (3): migration/dirtyrate: implement vCPU dirtyrate calculation periodically cpu-throttle: implement vCPU throttle cpus-common: implement dirty restraint on vCPU cpus-common.c | 45 ++++++ include/exec/memory.h | 5 +- include/hw/core/cpu.h | 7 + include/sysemu/cpu-throttle.h | 21 +++ include/sysemu/dirtyrestraint.h | 22 +++ migration/dirtyrate.c | 125 +++++++++++++++++ migration/dirtyrate.h | 2 + qapi/misc.json | 44 ++++++ softmmu/cpu-throttle.c | 304 ++++++++++++++++++++++++++++++++++++++++ softmmu/trace-events | 5 + softmmu/vl.c | 1 + 11 files changed, 580 insertions(+), 1 deletion(-) create mode 100644 include/sysemu/dirtyrestraint.h -- 1.8.3.1
