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Message-ID: <901aef4c-27fa-475f-9d56-7ee292cca763@intel.com>
Date: Thu, 1 Feb 2024 16:49:23 +0100
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Subject: Re: [PATCH net-next v5 01/21] lib/bitmap: add bitmap_{read,write}()
To: Arnd Bergmann <arnd@arndb.de>
CC: "David S . Miller" <davem@davemloft.net>, Eric Dumazet
	<edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni
	<pabeni@redhat.com>, Michal Swiatkowski <michal.swiatkowski@linux.intel.com>,
	Marcin Szycik <marcin.szycik@linux.intel.com>, Wojciech Drewek
	<wojciech.drewek@intel.com>, Yury Norov <yury.norov@gmail.com>, "Andy
 Shevchenko" <andy@kernel.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Alexander Potapenko <glider@google.com>, Jiri Pirko <jiri@resnulli.us>, "Ido
 Schimmel" <idosch@nvidia.com>, Przemek Kitszel
	<przemyslaw.kitszel@intel.com>, Simon Horman <horms@kernel.org>,
	<linux-btrfs@vger.kernel.org>, <dm-devel@redhat.com>,
	<ntfs3@lists.linux.dev>, <linux-s390@vger.kernel.org>,
	"intel-wired-lan@lists.osuosl.org" <intel-wired-lan@lists.osuosl.org>, Netdev
	<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>, Syed Nayyar Waris
	<syednwaris@gmail.com>, William Breathitt Gray <william.gray@linaro.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
References: <20240201122216.2634007-1-aleksander.lobakin@intel.com>
 <20240201122216.2634007-2-aleksander.lobakin@intel.com>
 <3f6df876-4b25-4dc8-bbac-ce678c428d86@app.fastmail.com>
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From: Alexander Lobakin <aleksander.lobakin@intel.com>
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From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 01 Feb 2024 14:23:33 +0100

> On Thu, Feb 1, 2024, at 13:21, Alexander Lobakin wrote:
>> From: Syed Nayyar Waris <syednwaris@gmail.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.

When their arguments are compile-time constants, they got optimized
well. They're also used on hotpath, so making them external could hurt
performance + taking the first sentence into account, making them
external will hurt the performance even more, 'cause they won't be then
as optimized by the compiler as they are now.

> 
> 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

Thanks,
Olek