linux-kernel - Re: [Patch] mm tracepoints

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Message-ID: <20090306135547.GB21907@elte.hu>
Date:	Fri, 6 Mar 2009 14:55:47 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Larry Woodman <lwoodman@...hat.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	fweisbec@...il.com, Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [Patch] mm tracepoints


* Larry Woodman <lwoodman@...hat.com> wrote:

> On Fri, 2009-03-06 at 12:04 +0100, Ingo Molnar wrote:
> > * Steven Rostedt <rostedt@...dmis.org> wrote:
> > 
> > > 
> > > On Fri, 6 Mar 2009, KOSAKI Motohiro wrote:
> > > 
> > > > > I've implemented several mm tracepoints to track page allocation and
> > > > > freeing, various types of pagefaults and unmaps, and critical page
> > > > > reclamation routines.  This is useful for debugging memory allocation
> > > > > issues and system performance problems under heavy memory loads:
> > > > > 
> > > > > # tracer: mm
> > > > > #
> > > > > #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
> > > > > #              | |       |          |         |
> > > > >          pdflush-624   [004]   184.293169: wb_kupdate:
> > > > > (mm_pdflush_kupdate) count=3e48
> > > > >          pdflush-624   [004]   184.293439: get_page_from_freelist:
> > > > > (mm_page_allocation) pfn=447c27 zone_free=1940910
> > > > >         events/6-33    [006]   184.962879: free_hot_cold_page:
> > > > > (mm_page_free) pfn=44bba9
> > > > >       irqbalance-8313  [001]   188.042951: unmap_vmas:
> > > > > (mm_anon_userfree) mm=ffff88044a7300c0 address=7f9a2eb70000 pfn=24c29a
> > > > >              cat-9122  [005]   191.141173: filemap_fault:
> > > > > (mm_filemap_fault) primary fault: mm=ffff88024c9d8f40 address=3cea2dd000
> > > > > pfn=44d68e
> > > > >              cat-9122  [001]   191.143036: handle_mm_fault:
> > > > > (mm_anon_fault) mm=ffff88024c8beb40 address=7fffbde99f94 pfn=24ce22
> > > > > ...
> > > > 
> > > > Hi Larry,
> > > > 
> > > > I've started to evaluate your patch.
> > > > 
> > > > firstly, this patch can't apply tip/master.
> > 
> > yeah, would be nice to have a patch against:
> > 
> >   http://people.redhat.com/mingo/tip.git/README
> 
> Yeah I'll fix that, it is a moving target.
> > 
> > > > secondly, I don't think the address of mm_struct and pfn 
> > > > help to analysis. administrator don't know the page is which 
> > > > file's cache.
> > > 
> > > The mm_struct may not be helpful since there should be a 1 to 
> > > 1 mapping between user tasks and the mm struct. Hmm, maybe 
> > > not, due to threads?
> > 
> > Correct - so the mm ID looks useful.
> > 
> > > But the pfn is helpful since it is a unique identifier for 
> > > what physical page was mapped.
> > 
> > Yeah. Nevertheless some sort of filename:offset indicator 
> > would be nice too. (as an add-on)
> 
> You mean in the filemap pagefault case???

Would that be useless or controversial? We know from 
vma->mapping which inode it maps to. Knowing which file is 
faulting in can be useful - especially when addresses are a 
moving target such as under PIE or with dlopen(), etc.

	Ingo
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