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Date:   Mon, 14 Aug 2023 15:28:41 +0300
From:   'Andy Shevchenko' <andriy.shevchenko@linux.intel.com>
To:     David Laight <David.Laight@aculab.com>
Cc:     'Petr Mladek' <pmladek@suse.com>, Marco Elver <elver@google.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 2/3] lib/vsprintf: Split out sprintf() and friends
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On Mon, Aug 14, 2023 at 08:12:55AM +0000, David Laight wrote:
> From: Andy Shevchenko
> > Sent: 10 August 2023 14:14
> > On Wed, Aug 09, 2023 at 08:48:54AM +0000, David Laight wrote:

...

> > > > If you split headers into so many small pieces then all
> > > > source files will start with 3 screens of includes. I do not see
> > > > how this helps with maintainability.
> > >
> > > You also slow down compilations.
> > 
> > Ingo's patches showed the opposite. Do you have actual try and numbers?
> 
> The compiler has to open the extra file on every compile.
> If you include it from lots of different places it has to open
> it for each one (to find the include guard).
> Any attempted compiler optimisations have the same much the
> same problem as #pragma once.
> 
> With a long -I list even finding the file can take a while.
> 
> Probably most obvious when using NFS mounted filesystems.
> Especially the 'traditional' NFS protocol that required a
> message 'round trip' for each element of the directory path.

Right, as I said come up with numbers. Ingo did that, so can you.
His numbers shows _increase_ of build speed.

-- 
With Best Regards,
Andy Shevchenko