Re: [PATCH 0/2] Build ORC fast lookup table in scripts/sorttable tool

Josh Poimboeuf
2020-04-30T04:10:44Z

On Wed, Apr 29, 2020 at 11:06:58PM -0500, Josh Poimboeuf wrote:
> On Thu, Apr 30, 2020 at 10:32:17AM +0800, changhuaixin wrote:
> >
> >
> > > On Apr 29, 2020, at 4:49 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > On Wed, Apr 29, 2020 at 02:46:24PM +0800, Huaixin Chang wrote:
> > >> Move building of fast lookup table from boot to sorttable tool. This saves us
> > >> 6380us boot time on Intel(R) Xeon(R) CPU E5-2682 v4 @ 2.50GHz with cores.
> > >
> > > And what does it add to the build time?
> >
> > It takes a little more than 7ms to build fast lookup table in
> > sorttable on the same CPU. And it is on the critical path.
>
> Thanks, I like it. It will help make the in-kernel unwinder even
> simpler. And it will enable unwinding from early boot.
>
> Maybe someday we can move all the table sorting code into objtool, once
> we have objtool running on vmlinux.o.
>
> I'll try to review the patches soon.

BTW, another cool feature would be for sorttable to run on modules
during the module linking phase.

--
Josh