On Wed, Jul 19, 2023 at 5:03 PM Markus Armbruster <arm...@redhat.com> wrote:
> Yong Huang <yong.hu...@smartx.com> writes: > > > On Wed, Jul 19, 2023 at 1:26 PM Markus Armbruster <arm...@redhat.com> > wrote: > > > >> Yong Huang <yong.hu...@smartx.com> writes: > >> > >> > On Tue, Jul 18, 2023 at 7:04 PM Markus Armbruster <arm...@redhat.com> > >> wrote: > >> > > >> >> Yong Huang <yong.hu...@smartx.com> writes: > >> >> > >> >> > On Thu, Jul 13, 2023 at 8:44 PM Markus Armbruster < > arm...@redhat.com> wrote: > > [...] > > >> >> Yes, please. But before that, I have still more questions. "This > >> >> algorithm only works when vCPU's dirtyrate greater than > >> >> 'vcpu-dirty-limit'" is a condition: "FEATURE only works when > CONDITION". > >> >> > >> > I failed to express my meaning again : ( . "Throttle algo only works > when > >> > vCPU's dirtyrate greater than 'vcpu-dirty-limit' " should change to > >> > "vCPU throttle only works when vCPU's dirtyrate greater than > >> > 'vcpu-dirty-limit'". > >> > Not the whole "algo" ! > >> > >> Let me paraphrase to make sure I got it... The vCPU is throttled as > >> needed to keep its dirty rate within the limit set with > >> set-vcpu-dirty-limit. Correct? > >> > > Yes. Actually set with the internal function qmp_set_vcpu_dirty_limit. > > > > And a parameter called "vcpu-dirty-limit" of migration provided by > > dirty-limit > > aims to be the argument of qmp_set_vcpu_dirty_limit. > > Alright, let me try to craft some documentation: > > # @dirty-limit: If enabled, migration will throttle vCPUs as needed to > # keep their dirty page rate within @vcpu-dirty-limit. This can > # improve responsiveness of large guests during live migration, > # and can result in more stable read performance. Requires KVM > # with accelerator property "dirty-ring-size" set. (Since 8.1) > > What do you think? > I feel ok, it seems clear and concise. I'll use this comment in the next version. Thanks a lot. :) > > >> What happens when I enable the dirty limit convergence algorithm without > >> setting a limit with set-vcpu-dirty-limit? > >> > > dirty-limit will use the default value which is defined > > in migration/options.c: > > #define DEFAULT_MIGRATE_VCPU_DIRTY_LIMIT 1 /* MB/s */ > > > > So the default of the dirty-limit is 1MB/s. > > Is this default documented in the QAPI schema? Hmm, looks like it isn't > before this series, but PATCH 3 fixes it. Okay. > > >> >> What happens when the condition is not met? How can the user ensure > the > >> >> condition is met? > >> >> > >> >> [...] > > -- Best regards
