linux-kernel - Re: S390: Fine-tuning for six function implementations

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Date:   Tue, 9 May 2017 10:43:56 +0200
From:   SF Markus Elfring <elfring@...rs.sourceforge.net>
To:     Vegard Nossum <vegard.nossum@...cle.com>,
        linux-s390@...r.kernel.org
Cc:     Christian Bornträger <borntraeger@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sascha Silbe <silbe@...ux.vnet.ibm.com>,
        Viktor Mihajlovski <mihajlov@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: S390: Fine-tuning for six function implementations

> It would be different if your patches fixed actual bugs.

I dare to point change possibilities out which correspond to a special error category.
There can be different opinions about their relevance for further software improvements.

> This is just mindless code transformations that MAY in the best case save a few bytes
> of code here and there (I don't know; you didn't say).

Do you know the run time characteristics for the discussed functions good enough?
http://elixir.free-electrons.com/linux/v4.11/source/fs/seq_file.c#L405

> But the potential gains from these incredibly numerous and tiny patches
> that don't fix anything are so small, it's a waste of time, bandwidth,
> and mental capacity for you and for everybody involved.

I suggest a bit of code reduction at various places once more.

> I just searched my inbox for patches from you and you sent literally
> _hundreds_ over the past few days,

I sent update suggestions in this scale since the year 2014.

> all doing this crazy printf/puts/putc transformation.

I agree that the corresponding number could be remarkable.
But there are also other source code search patterns involved besides information
around these logging functions.

> Another bit of searching and I see that I'm not the first one giving you
> this response:

You are right that some agreements and disagreements were expressed already
(depending on the software area).

Regards,
Markus