linux-kernel - Re: [PATCH 3/3] lib: vsprintf: added a put

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Message-ID: <8762zn7mzu.fsf@hariville.hurrynot.org>
Date:	Fri, 06 Aug 2010 21:27:09 +0530
From:	Raja R Harinath <harinath@...rynot.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] lib: vsprintf: added a put_dec() test and benchmark tool

Hi,

Michał Nazarewicz <m.nazarewicz@...sung.com> writes:

> On Fri, 06 Aug 2010 07:10:06 +0200, Denys Vlasenko <vda.linux@...glemail.com> wrote:
>
>> On Friday 06 August 2010 00:38, Michal Nazarewicz wrote:
>>> This commit adds a test application for the put_dec() and
>>> family of functions that are used by the previous two commits.
>>>
>>> Signed-off-by: Michal Nazarewicz <mina86@...a86.com>
>>
>>> +put-dec-test: put-dec-test.c
>>> +	exec $(CC) $(CFLAGS) -o $@ $<
>>
>> (1) Why exec?
>
> Micro Makefile optimisation -- saves us a fork().

I don't think it's worth it.  The use of 'exec' will force make to
invoke the shell, while without the exec, make has an opportunity to
optimize out the shell invocation completely [1].  Forcing the use of a
shell to avoid a fork() sounds like a terrible trade-off.

- Hari

[1] See, for instance, construct_command_argv_internal() in

  http://cvs.savannah.gnu.org/viewvc/make/job.c?root=make&view=markup

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