linux-kernel - Re: [RFC] [Patch 4/4] lock contention tracking slimmed down

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Date:	Thu, 07 Jun 2007 02:17:45 +0200
From:	Martin Peschke <mp3@...ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	jbaron@...hat.com, rostedt@...dmis.org, linux-s390@...r.kernel.org
Subject: Re: [RFC] [Patch 4/4] lock contention tracking slimmed down

Ingo Molnar wrote:
> * Martin Peschke <mp3@...ibm.com> wrote:
> 
>> The output has changed from a terribly wide table to an enormously 
>> long list (just the generic way the statistics code prints data). 
> 
> Sigh, why dont you _ask_ before doing such stuff?

A nice diffstat is always worth a try, isn't it?
And I see other reasons for code sharing.
Ah, and doing it has been actually quite simple once I had figured out
what the original code does. :-)

> It is a terribly wide table because that makes it easily greppable

If one looks for contentions of "xtime_lock" within my enormously long list,
they could issue:

    grep -e "xtime_lock contentions" data

and get

    xtime_lock contentions 0x17bd2 3327 account_ticks+0x96/0x184
    xtime_lock contentions other 0

for example.

So how is this worse?

> but still watchable in one chunk in a sufficiently zoomed out xterm.

I am wondering whether we really want to reject kernel patches on the basis of 
this reasoning, disregarding any other point why a patch might be helpful.

 > Please preserve this output format

I understand why everybody likes their format most. It's always made to measure.
Chosing a different - or common - format didn't happen in bad faith.

Made to measure file format doesn't work well once we start abstracting out this 
functionality. And I feel that was expected too much of a low level kernel ABI 
piece.

I would like to add that usuability doesn't necessarily suffer if statistics for 
some brand new gadget look somewhat familiar and similar to other statistics one 
  has encountered earlier.

>, quite some work went into it - NACK :-(

Considering the amount of code.. ;-)    I am sorry.

But seriously, did you consider using some user space tool or script to
format this stuff the way you like it - similar to the way the powertop tool
reshuffles timer_stats data found in a proc file, for example?

The format of an enormously long list has been thought out keeping this 
particular requirement in mind.

	Martin

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