linux-kernel - Re: PROPOSAL: extend pipe() to support NULL argument.

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Message-ID: <20090703030008.GD5880@cr0.nay.redhat.com>
Date:	Fri, 3 Jul 2009 11:00:08 +0800
From:	Amerigo Wang <xiyou.wangcong@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Amerigo Wang <xiyou.wangcong@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: PROPOSAL: extend pipe() to support NULL argument.

On Fri, Jul 03, 2009 at 10:10:13AM +0800, Changli Gao wrote:
>On Fri, Jul 3, 2009 at 9:55 AM, Amerigo Wang<xiyou.wangcong@...il.com> wrote:
>>
>>
>> What is a pipe in your mind? A pipe has two points, obviously,
>> you are making it a single point, thus you can't call it a pipe
>> any more...
>>
>> I don't like this
>How do you think the following code?
>
>mkfifo("/tmp/a", O_RDWR);
>fd = open("'/tmp/a", O_RDWR);
>
>Is it right? Is it allowed by Linux/Unix/POSIX?
>
>and when used by splice(), pipe represents a kernel buffer handler not
>its original meaning.

When I said 'pipe', I meant *anonymous* pipe, definitely!
There is nothing related with *named* pipe here.

You are going to a *wrong* direction.

>.
>>
>> And just as what you showed above, you can close the fd's
>> after finishing, thus you only save one fd during these
>> two splice(), not useful...
>splice() is a high performance system call. It maybe used in thousands
>of connection environment, so one instance saves one fd, and thousands
>of fd will be saved.

If you repeat your (pipe,splice,splice,close,close) sequence for
thousands times, it is still the same, nothing saves...
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