linux-kernel - Re: [PATCH] new kfifo API v.08 (fixed)

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Date:	Mon, 21 Dec 2009 09:10:24 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Stefani Seibold <stefani@...bold.net>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andi Kleen <andi@...stfloor.org>,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	Joe Perches <joe@...ches.com>,
	Roger Quadros <quadros.roger@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Shargorodsky Atal <ext-atal.shargorodsky@...ia.com>
Subject: Re: [PATCH] new kfifo API v.08 (fixed)

Stefani Seibold wrote:
> This is a complete rewrite of the new kfifo API, which is now really
> generic. The API is still stable. 
> 
> There are different types of a fifo which can not handled in C without a
> lot of overhead. So i decided to write the API as a set of macros, which 
> is the only way to do a kind of template meta programming without c++. 
> This macros handles the different types of fifos in a transparent way.
> 
> There are a lot of benefits:
> 
> - Compile time handling of the different fifo types
> - Performance (a save put or get of an integer does only generate 9 assembly
>   instructions on a x86) 
> - Type save
> - Cleaner interface, the additional kfifo_..._rec() functions are gone
> - Easier to use
> - Less error prone
> - Smaller footprint
> - Different types of fifos: it is now possible to define a int fifo or
>   any other type. See below for an example.
> - The size of the record field will be now detected at compile time
> - No need of creating a hidden variable, like in DEFINE_KFIFO
> 
> The API has not been change, but there are now real in place fifos
> where the data space is a part of the structure. There is no need for an
> extra indirection to the access the data and also no size field, because
> the size of the fifo can be determinate with sizeof. This kind of fifo
> does only need 8 bytes plus the fifo space.
> 
> The dynamic assigned or allocated fifos still needs 16 byte plus the 
> fifo space and does also creates more code.
> 
> Most of the macros code will be optimized away and does only generate a 
> function call.  Only the really the small ones generates inline code. The 
> overall size is half of the size of the previous implementation.
> 
> Additional you can now create fifos for any data type, not only the
> "unsigned char" byte streamed fifos.
> 
> There is also a new kfifo_put and kfifo_get function, to handle a single
> element in a fifo.
> 
> Here is a small example how to use it:
> 
> Example 1: an integer fifo
> 

Why don't you put those examples into samples/kfifo/ ?

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