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Date: Thu, 10 Jan 2013 10:16:46 -0500
From: Alfred Perlstein <bright@mu.org>
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To: Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: malloc+utrace, tracking memory leaks in a running program.
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Cc: Daniel Eischen <deischen@freebsd.org>, hackers@freebsd.org,
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On 1/10/13 2:38 AM, Konstantin Belousov wrote:
> On Thu, Jan 10, 2013 at 01:56:48AM -0500, Alfred Perlstein wrote:
>> Here are more convenient links that give diffs against FreeBSD and
>> jemalloc for the proposed changes:
>>
>> FreeBSD:
>> https://github.com/alfredperlstein/freebsd/compare/13e7228d5b83c8fcfc63a0803a374212018f6b68~1...utrace2
>>
> Why  do you need to expedite the records through the ktrace at all ?
> Wouldn't direct write(2)s to a file allow for better performance
> due to not stressing kernel memory allocator and single writing thread ?
> Also, the malloc coupling to the single-system interface would be
> prevented.
>
> I believe that other usermode tracers also behave in the similar way,
> using writes and not private kernel interface.
>
> Also, what /proc issues did you mentioned ? There is
> sysctl kern.proc.vmmap which is much more convenient than /proc/pid/map
> and does not require /proc mounted.
>
>> jemalloc:
>> https://github.com/alfredperlstein/jemalloc/compare/master...utrace2
>>

Konstantin, you are right, it is a strange thing this utrace.  I am not 
sure why it was done this way.

You are correct in that much more efficient system could be made using 
writes gathered into a single write(2).

Do you think there is any reason they may have re-used the kernel paths 
for ktrace even at the cost of efficiency?

About kern.proc.vmmap I will look into that.

-Alfred