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To: Robert Watson <rwatson@FreeBSD.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 12 Apr 2009 15:28:48 +0100."
	<alpine.BSF.2.00.0904121525540.19879@fledge.watson.org> 
Date: Sun, 12 Apr 2009 15:11:54 +0000
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
	src-committers@FreeBSD.org, Luigi Rizzo <rizzo@iet.unipi.it>
Subject: Re: per-cpu counters (Re: svn commit: r190967 - head/sys/netinet) 
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In message <alpine.BSF.2.00.0904121525540.19879@fledge.watson.org>, Robert Wats
on writes:

>I have a project along these lines in progress, and will post the proposal to 
>arch@ once I've finished prototyping it.  In particular, it provides common 
>implementations of "reset" and "report" in order to expose a single userspace 
>version of the structure via sysctl.

Please don't export them via sysctl.

Export them via mmap(2) like we already do with the disk I/O statistics.

That way monitoring the counters becomes a no-syscall operation.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.