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

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Message-ID: <20200430040654.mnkcfmj32tr6m3mg@treble>
Date:   Wed, 29 Apr 2020 23:06:54 -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 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.

-- 
Josh