From: Keith Busch <kbusch@kernel.org>
To: Caleb Sander Mateos <csander@purestorage.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Anuj Gupta <anuj20.g@samsung.com>
Subject: Re: [PATCH v2] t10-pi: reduce ref tag code duplication
Date: Fri, 17 Apr 2026 10:52:09 -0600 [thread overview]
Message-ID: <aeJlOZ3OwyJH6iAw@kbusch-mbp> (raw)
In-Reply-To: <CADUfDZqDz9a4yBOq77mTOjQzNEwra6eh6oZFng-mzjmC5ivD8g@mail.gmail.com>
On Fri, Apr 17, 2026 at 08:34:30AM -0700, Caleb Sander Mateos wrote:
> On Fri, Apr 17, 2026 at 12:56 AM Christoph Hellwig <hch@infradead.org> wrote:
> > folks out there actually dropping not needed includes from headers as
> > it can significantly reduce compile time. Now this is not a heavily
> > included header so it's unlikely to make a difference anyway.
>
> Is a file being included by the preprocessor multiple times really
> that expensive? I would have assumed it would be cached the first time
> it was included.
Do modern compilers even incur a cost? They all have "multiple-include
optimization" features as far as i know. Not that we use "#prama once"
in kernel, but compilers look like they're smart enough to recognize the
#ifdef guards for the same purpose.
https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html#The-Multiple-Include-Optimization
next prev parent reply other threads:[~2026-04-17 16:52 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-15 21:08 [PATCH v2] t10-pi: reduce ref tag code duplication Caleb Sander Mateos
2026-04-16 5:18 ` Christoph Hellwig
2026-04-16 15:38 ` Caleb Sander Mateos
2026-04-17 7:56 ` Christoph Hellwig
2026-04-17 15:34 ` Caleb Sander Mateos
2026-04-17 16:52 ` Keith Busch [this message]
2026-04-17 20:39 ` Jens Axboe
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