Re: [GIT PULL] Clang feature updates for v5.14-rc1

[Peter Zijlstra]

On Fri, Jul 02, 2021 at 10:26:40AM -0700, Nick Desaulniers wrote:
> On Fri, Jul 2, 2021 at 5:57 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> > I've asked this before; *what* is missing from LBR samples that's
> > reponsible for the performance gap?
> 
> Are we able to collect LBR samples from __init code?  I can imagine
> trying to launch perf from init/pid 1, but I suspect at that point
> it's way too late.
> 
> Increasingly, boot times of hosts (and virtualized guests) are
> becoming important to us, both in the datacenters and on mobile.

For a guest, possibly, I've no idea how any of that virt crud works.