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From: John Baldwin <jhb@freebsd.org>
To: freebsd-hackers@freebsd.org
Subject: Re: libprocstat(3): retrieve process command line args and environment
Date: Tue, 22 Jan 2013 12:01:06 -0500
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 (bigwig.baldwin.cx); Tue, 22 Jan 2013 12:14:53 -0500 (EST)
Cc: Mikolaj Golub <trociny@freebsd.org>, Stanislav Sedov <stas@freebsd.org>,
 Robert Watson <rwatson@freebsd.org>
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On Saturday, January 19, 2013 10:12:54 am Mikolaj Golub wrote:
> Hi,
> 
> Some time ago Stanislav Sedov suggested to me extending libprocstat(3)
> with functions to retrieve process command line arguments and
> environment variables.
> 
> In the first approach I tried, the newly added functions
> procstat_getargv/getenvv allocated a buffer of necessary size, stored
> the values and returned to the caller:
> 
> http://people.freebsd.org/~trociny/libprocstat.1.patch
> 
> The problem with this approach was that when I updated procstat(1) to
> use this interface, I observed noticeable performance degradation
> (about 30% on systems with MALLOC_PRODUCTION off), due to memory
> allocation overhead: the original procstat(1) reuses the buffer for
> all its retrievals.
> 
> So my second approach was to add internal buffers to struct procstat,
> which are used by procstat_getargv/getenvv to store values and reused
> on the subsequent call:
> 
> http://people.freebsd.org/~trociny/libprocstat.2.patch
> 
> The drawback of this approach is that a user has to take care and
> remember that a subsequent call rewrites argument vector obtained from
> the previous call. On the other hand this is ok for typical use cases
> while does not add allocation overhead, so I like this approach more.
> 
> I would like to commit this second patch, if there are no objections
> or suggestions how to improve the things.

How is this different from kvm_getargv()?  It seems to be a direct copy.

-- 
John Baldwin