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From: Linus Torvalds <torvalds@linuxfoundation.org>
To: David Laight <David.Laight@aculab.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	 "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Christoph Hellwig <hch@infradead.org>,
	 Andrew Morton <akpm@linux-foundation.org>,
	 Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	 Dan Carpenter <dan.carpenter@linaro.org>,
	Arnd Bergmann <arnd@kernel.org>,
	 "Jason@zx2c4.com" <Jason@zx2c4.com>,
	"pedro.falcato@gmail.com" <pedro.falcato@gmail.com>,
	 Mateusz Guzik <mjguzik@gmail.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	 Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Subject: Re: [PATCH v2 1/8] minmax: Put all the clamp() definitions together
Date: Sun, 28 Jul 2024 15:22:58 -0700	[thread overview]
Message-ID: <CAHk-=wicdsz3bvy9g7RJ_XvugjxAT0XDitwTQLZmxq40JtHbzg@mail.gmail.com> (raw)
In-Reply-To: <b89b80c7060c43f8a937b8021b4fd7cb@AcuMS.aculab.com>

On Sun, 28 Jul 2024 at 15:14, David Laight <David.Laight@aculab.com> wrote:
>
> Ok, but those can't be used as array sizes or constants.
> So the temporaries don't matter.

No, mut I don't want the insane size explosion from unnecessarily just
forcing it to use min()/max().

> Don't they just work with min() - if not where is the signednes mismatch?

David - this whole discussion is BECAUSE THESE THINGS ARE A TOTAL
DISASTER WHEN USED IN DEEP MACRO EXPANSION.

So no. It does not work - because core macros like HUGETLB_PAGE_ORDER
end up being used deep in the VM layer, and I don't want to see
another stupid multi-ten-kB line just because min() is such a pig.

End result: I'm going to make the rule be that when you do macro
definitions using constants, then "MIN()/MAX()" is preferable simply
because it avoids the insane expansion noise.

Then in normal *code* you should use min() and max(). But not for
things like macro "constants" even if those constants end up being
some computed thing.

          Linus


  reply	other threads:[~2024-07-28 22:23 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-07-28 14:15 [PATCH v2 0/8] minmax: reduce compilation time David Laight
2024-07-28 14:17 ` [PATCH v2 1/8] minmax: Put all the clamp() definitions together David Laight
2024-07-28 17:24   ` Linus Torvalds
2024-07-28 18:11     ` David Laight
2024-07-28 19:55       ` Linus Torvalds
2024-07-28 20:09         ` David Laight
2024-07-28 20:13           ` Linus Torvalds
2024-07-28 20:22             ` David Laight
2024-07-28 20:31               ` Linus Torvalds
2024-07-28 22:13                 ` David Laight
2024-07-28 22:22                   ` Linus Torvalds [this message]
2024-07-29  8:01                     ` David Laight
2024-07-28 21:01               ` Linus Torvalds
2024-07-28 21:53                 ` David Laight
2024-07-29  4:15                 ` Linus Torvalds
2024-07-29 22:25             ` Arnd Bergmann
2024-07-29 23:21               ` Linus Torvalds
2024-07-30  1:52                 ` Linus Torvalds
2024-07-30  3:59                 ` Linus Torvalds
2024-07-30 10:10                   ` Arnd Bergmann
2024-07-30 14:14                     ` Arnd Bergmann
2024-07-30 18:02                       ` Linus Torvalds
2024-07-30 19:52                         ` Linus Torvalds
2024-07-30 21:47                           ` David Laight
2024-07-30 22:44                             ` Linus Torvalds
2024-07-30 23:03                               ` Linus Torvalds
2024-07-31  8:09                                 ` David Laight
2024-07-31 10:50                                   ` Arnd Bergmann
2024-07-31 15:38                                   ` Linus Torvalds
2024-07-31 15:56                                     ` David Laight
2024-07-31 16:04                                       ` Linus Torvalds
2024-12-04 13:15                       ` Geert Uytterhoeven
2024-12-04 17:16                         ` David Laight
2024-07-30 16:35                     ` Linus Torvalds
2024-07-30 16:46                       ` Linus Torvalds
2024-07-30 12:03               ` David Laight
2024-07-28 18:23     ` David Laight
2024-07-28 14:18 ` [PATCH v2 2/8] minmax: Use _Static_assert() instead of static_assert() David Laight
2024-07-28 17:51   ` Christophe JAILLET
2024-07-28 18:12     ` David Laight
2024-07-28 14:19 ` [PATCH v2 3/8] compiler.h: Add __if_constexpr(expr, if_const, if_not_const) David Laight
2024-07-28 14:20 ` [PATCH v2 4/8] minmax: Simplify signedness check David Laight
2024-07-28 16:57   ` Linus Torvalds
2024-07-28 18:14     ` David Laight
2024-07-28 20:13       ` David Laight
2024-07-28 14:21 ` [PATCH v2 5/8] minmax: Factor out the zero-extension logic from umin/umax David Laight
2024-07-28 14:22 ` [PATCH v2 6/8] minmax: Optimise _Static_assert() check in clamp() David Laight
2024-07-28 14:23 ` [PATCH v2 7/8] minmax: Use __auto_type David Laight
2024-07-28 16:59   ` Linus Torvalds
2024-07-28 14:24 ` [PATCH v2 8/8] minmax: minmax: Add __types_ok3() and optimise defines with 3 arguments David Laight

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