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

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Message-ID: <20200430041033.x7hggzh2lsbtc3u7@treble>
Date:   Wed, 29 Apr 2020 23:10:33 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     changhuaixin <changhuaixin@...ux.alibaba.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        bp@...en8.de, hpa@...or.com, luto@...capital.net,
        michal.lkml@...kovi.net, mingo@...hat.com, tglx@...utronix.de,
        x86@...nel.org, yamada.masahiro@...ionext.com
Subject: Re: [PATCH 0/2] Build ORC fast lookup table in scripts/sorttable tool

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@...radead.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