linux-kernel - Re: [PATCH v2 2/2] scripts: ftrace - move the nop-processing in ftrace

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Date:   Tue, 16 Nov 2021 20:51:18 +0800
From:   Yinan Liu <yinan@...ux.alibaba.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     rostedt@...dmis.org, mark-pk.tsai@...iatek.com, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] scripts: ftrace - move the nop-processing in
 ftrace_init to compile time


在 2021/11/16 下午4:10, Peter Zijlstra 写道:
> On Tue, Nov 16, 2021 at 10:49:42AM +0800, Yinan Liu wrote:
>> In some business scenarios, GCC versions are so old that
>> optimizations in ftrace cannot be completed, such as
>> -mrecord-mcount and -mnop-mcount. The recordmCount in the
>> kernel is actually used. In this case, ftrace_init will
>> consume a period of time, usually around 9~12ms. Do nop
>> substitution in recordmcount.c to speed up ftrace_init.
> 
> I really don't buy this.. if you can build a fresh kernel, you can
> install a fresh gcc too -- and if you care about performance that's a
> very good idea anyway.
> 
Thanks! You are right. We should get rid of the burden.