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Subject: Re: [PATCH] performance counters 3.1 for 2.5.45 [4/4]: kernel
	changes
From: Stephen Hemminger <shemminger@osdl.org>
To: Mikael Pettersson <mikpe@csd.uu.se>
Cc: Linus Torvalds <torvalds@transmeta.com>,
       Kernel List <linux-kernel@vger.kernel.org>
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On Mon, 2002-11-04 at 12:31, Mikael Pettersson wrote:
> Stephen Hemminger writes:
>  > On Thu, 2002-10-31 at 15:10, Mikael Pettersson wrote:
>  > > This is part 4 of 4 of perfctr-3.1 for the 2.5.45 kernel:
>  > > kernel changes to integrate the low and high-level drivers.
> ...
>  > 
>  > Rather than adding yet another system call, shouldn't this be done by
>  > extending the cpu part of sysfs (or /proc)?
> 
> Why?
> ptrace() is a system call
> fork() is a system call
> write() is a system call
> other arch's performance counter interfaces are system calls
> ...

ptrace predates /proc, and /proc is gradually superseding ptrace.
Eventually it is hoped that ptrace dies.

Other architecture's added performance counters back in 2.4 before sysfs
was added.

The reason to use a file system rather than a syscall is so that
standard tools like sh, awk, perl, ... can be used on the data without
having to build a separate command to access the data.

Linus is more likely to adopt simpler logical interfaces.


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