Re: [PATCH v2 1/7] sched/fair: Fix zero_vruntime tracking

[Steven Rostedt]

On Mon, 30 Mar 2026 10:58:54 -0700
John Stultz <jstultz@xxxxxxxxxx> wrote:


> Nice. I've actually been using ftrace_dump_on_oops as I log the VM
> serial console to a file and don't have to remember to go fetch it out
> the next time. But this is helpful when its on real hardware (dumping
> the trace over serial console can take awhile and I've had cases where
> the hardware watchdogs reboot the device midway when the trace is too
> large).
>

I use it on VMs all the time. It works nicely with qemu.

In the near future we will have a backup buffer implementation too, where
you don't need to remember to start it!

  reserve_mem=100M:12M:trace trace_instance=boot_mapped^traceprintk^@trace trace_instance=backup=boot_mapped

Where on early boot up, a "backup" instance is created and copies the
persistent ring buffer to a read-only temporary buffer that doesn't get
overwritten.

Then you can keep the persistent ring buffer always on, and if there's a
crash, just look at the "backup" instance to see what happened.

-- Steve