linux-kernel - Re: [PATCH net-next v5 01/21] lib/bitmap: add bitmap

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Date: Thu, 1 Feb 2024 14:45:58 +0100
From: Alexander Potapenko <glider@...gle.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>, 
	Marcin Szycik <marcin.szycik@...ux.intel.com>, Wojciech Drewek <wojciech.drewek@...el.com>, 
	Yury Norov <yury.norov@...il.com>, Andy Shevchenko <andy@...nel.org>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Jiri Pirko <jiri@...nulli.us>, 
	Ido Schimmel <idosch@...dia.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
	Simon Horman <horms@...nel.org>, linux-btrfs@...r.kernel.org, dm-devel@...hat.com, 
	ntfs3@...ts.linux.dev, linux-s390@...r.kernel.org, 
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>, Netdev <netdev@...r.kernel.org>, 
	linux-kernel@...r.kernel.org, Syed Nayyar Waris <syednwaris@...il.com>, 
	William Breathitt Gray <william.gray@...aro.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH net-next v5 01/21] lib/bitmap: add bitmap_{read,write}()

On Thu, Feb 1, 2024 at 2:23 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Feb 1, 2024, at 13:21, Alexander Lobakin wrote:
> > From: Syed Nayyar Waris <syednwaris@...il.com>
> >
> > The two new functions allow reading/writing values of length up to
> > BITS_PER_LONG bits at arbitrary position in the bitmap.
> >
> > The code was taken from "bitops: Introduce the for_each_set_clump macro"
> > by Syed Nayyar Waris with a number of changes and simplifications:
> >  - instead of using roundup(), which adds an unnecessary dependency
> >    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
> >  - indentation is reduced by not using else-clauses (suggested by
> >    checkpatch for bitmap_get_value());
> >  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
> >    and bitmap_write();
> >  - some redundant computations are omitted.
>
> These functions feel like they should not be inline but are
> better off in lib/bitmap.c given their length.
>
> As far as I can tell, the header ends up being included
> indirectly almost everywhere, so just parsing these functions
> likey adds not just dependencies but also compile time.
>
>      Arnd

Removing particular functions from a header to reduce compilation time
does not really scale.
Do we know this case has a noticeable impact on the compilation time?
If yes, maybe we need to tackle this problem in a different way (e.g.
reduce the number of dependencies on it)?