linux-kernel - RE: [PATCH v4 2/7] kernel.h: Split out container_of() and typeof

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Message-ID: <33e1be3f6e3b40eeb6f3cd5524e649fe@AcuMS.aculab.com>
Date:   Mon, 11 Oct 2021 09:07:10 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Joe Perches' <joe@...ches.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "kunit-dev@...glegroups.com" <kunit-dev@...glegroups.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
CC:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "linux@...musvillemoes.dk" <linux@...musvillemoes.dk>,
        Thorsten Leemhuis <regressions@...mhuis.info>
Subject: RE: [PATCH v4 2/7] kernel.h: Split out container_of() and
 typeof_member() macros

From: Joe Perches
> Sent: 07 October 2021 17:28
...
> IMO: this new file is missing 2 #include directives.
...
> This is not a self-contained header as it requires
> #include <linux/build_bug.h>
> which should be at the top of this file.
...
> And this requires
> 
> #include <linux/err.h>

And I bet the biggest problem is the time spent by the compiler
searching down the -I path for headers.

If you count system calls during a build I suspect that
failed opens of .h files dominate.

To see how much this really costs try running a build with
a (traditional) NFS mounted source tree - where every directory
name in a filename requires an NFS file handle lookup.

	David

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