On Wed, 07 Dec 2022 10:16:17 +0000, "chenxiang (M)" <chenxiang66@xxxxxxxxxxxxx> wrote: > > > > 在 2022/12/7 16:21, Marc Zyngier 写道: > > On Tue, 06 Dec 2022 12:58:26 +0000, > > chenxiang <chenxiang66@xxxxxxxxxxxxx> wrote: > >> From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx> > >> > >> Currently it only records statistical data for all vcpus, but we ofen want > >> to know statistical data for a single vcpu, there is no debugfs for that. > >> So add vcpu debugfs to record statstical data for every single vcpu, and > >> also enable vcpu debugfs for arm64. > >> > >> After the change, those vcpu debugfs are as follows (we have 4 vcpu in the > >> vm): > >> > >> [root@centos kvm]# cd 2025-14/ > >> [root@centos 2025-14]# ls > >> blocking halt_wait_hist vcpu0 > >> exits halt_wait_ns vcpu1 > >> halt_attempted_poll halt_wakeup vcpu2 > >> halt_poll_fail_hist hvc_exit_stat vcpu3 > >> halt_poll_fail_ns mmio_exit_kernel vgic-state > >> halt_poll_invalid mmio_exit_user wfe_exit_stat > >> halt_poll_success_hist remote_tlb_flush wfi_exit_stat > >> halt_poll_success_ns remote_tlb_flush_requests > >> halt_successful_poll signal_exits > >> [root@centos 2025-14]# cat exits > >> 124689 > >> [root@centos 2025-14]# cat vcpu0/exits > >> 52966 > >> [root@centos 2025-14]# cat vcpu1/exits > >> 21549 > >> [root@centos 2025-14]# cat vcpu2/exits > >> 43864 > >> [root@centos 2025-14]# cat vcpu3/exits > >> 6572 > >> [root@centos 2025-14]# ls vcpu0 > >> blocking halt_poll_invalid halt_wait_ns pid > >> exits halt_poll_success_hist halt_wakeup signal_exits > >> halt_attempted_poll halt_poll_success_ns hvc_exit_stat wfe_exit_stat > >> halt_poll_fail_hist halt_successful_poll mmio_exit_kernel wfi_exit_stat > >> halt_poll_fail_ns halt_wait_hist mmio_exit_user > > This is yet another example of "KVM doesn't give me the stats I want, > > so let's pile more stats on top". This affects every users (counters > > are not free), and hardly benefits anyone. > > Currently it already has vcpu debugfs on top, but it only records > statstical data for total vm > which is helpless for debug, for example, file exists records the > number of VM exist for all vcpus, before we encountered a > issue that there is something wrong with the thread of a vcpu which > doesn't VM exit but other vcpus are normal, > we can't get anything useful from current vcpu debugfs as the number > of exits still increase in current vcpu debugfs. > Compared with current vcpu debugfs, i think it is more useful to know > the statstical data for every vcpu and it benefits more. What is useful for you is useless for somebody else. And vice versa. At the end of the day, this is *debug* stuff. Why should a normal user pay a price for *debug* counters? > > How about you instead add trace hooks that allows you to plumb your > > own counters using BPF or another kernel module? This is what is stuff > > is for, and we really don't need to create more ABI around that. At > > least, the other stat-hungry folks out there would also be able to get > > their own stuff, and normal users wouldn't be affected by it. The answer to your problems is ^^^HERE^^^. M. -- Without deviation from the norm, progress is not possible.
