linux-kernel - Re: [Patch] mm tracepoints

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Date:	Fri, 6 Mar 2009 18:46:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Larry Woodman <lwoodman@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, fweisbec@...il.com
Subject: Re: [Patch] mm tracepoints


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Fri, 2009-03-06 at 18:10 +0100, Ingo Molnar wrote:
> > Looks pretty good and useful to me. I've Cc:-ed more mm folks, 
> > it would be nice to hear their opinion about these tracepoints.
> > 
> > Andrew, Nick, Peter, what do you think?
> 
> Bit sad we use the struct mm_struct * as mm identifier (little 
> %lx vs %p confusion there too), but I suppose there simply 
> isn't anything better.

the other option would be to trace the pgd physical pfn value. 
The physical address of the pagetable is a pretty fundamental 
thing so that abstraction is unlikely to change.

> Exposing kernel pointers like that might upset some of the 
> security folks, not sure if I care though.

it's admin-only.

> I'm missing the fault_filemap_read counterpart of 
> fault_anon_pgin.
> 
> Once you have anon/filemap symmetric, you might consider 
> folding these and doing the anon argument thing you do 
> elsewhere.
> 
> Initially I was thinking we lacked the kswapd vs direct 
> reclaim information on the pgout data, but since we log the 
> pid:comm for each event...
> 
> Which brings us to mm_pdflush_*, we can already see its 
> pdflush from pid:comm, then again, it fits the naming style. 
> Same for mm_directreclaim*() - we already know its direct, 
> since its not kswapd doing it.
> 
> Finally, we have page_free, but not page_alloc? Oh, it is 
> there, just not in the obvious place.
> 
> Things missing, we trace unmap, but not mmap, mprotect, mlock?
> 
> pagelock perhaps?

yeah, pagelock would be nice. In a similar way to lockdep 
tracing. Maybe it should be part of lock tracing?

	Ingo
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