linux-kernel - Re: [PATCH 6/6] perf: Add dcacheline sort

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Date:	Fri, 16 May 2014 16:05:51 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	acme@...stprotocols.net, peterz@...radead.org,
	LKML <linux-kernel@...r.kernel.org>, namhyung@...il.com,
	eranian@...gle.com, Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 6/6] perf: Add dcacheline sort

On Fri, May 16, 2014 at 09:30:58AM -0400, Don Zickus wrote:
> On Fri, May 16, 2014 at 01:47:57PM +0200, Jiri Olsa wrote:
> > On Tue, May 13, 2014 at 12:48:17PM -0400, Don Zickus wrote:
> > > In perf's 'mem-mode', one can get access to a whole bunch of details specific to a
> > > particular sample instruction.  A bunch of those details relate to the data
> > > address.
> > > 
> > > One interesting thing you can do with data addresses is to convert them into a unique
> > > cacheline they belong too.  Organizing these data cachelines into similar groups and sorting
> > > them can reveal cache contention.
> > > 
> > > This patch creates an alogorithm based on various sample details that can help group
> > > entries together into data cachelines and allows 'perf report' to sort on it.
> > > 
> > > The algorithm relies on having proper mmap2 support in the kernel to help determine
> > > if the memory map the data address belongs to is private to a pid or globally shared.
> > > 
> > > The alogortithm is as follows:
> > > 
> > > o group cpumodes together
> > > o group entries with discovered maps together
> > > o sort on major, minor, inode and inode generation numbers
> > > o if userspace anon, then sort on pid
> > > o sort on cachelines based on data addresses
> > 
> > needs some collumn width refresh or something..? ;-)
> 
> Not sure what you mean here.
> 
> > 
> > # Overhead  Data Cacheline         
> > # ........  .......................

header not being wide enough to cover the longest data


> > #
> >      5.42%  [k] 0xffff8801ed832c40 
> >      5.29%  [.] sys_errlist@@GLIBC_2.12+0xffffffcbf7dfc1ff                       
> >      3.16%  [k] 0xffffffffff5690c0 
> > 
> > 
> > also I've got again perf hanged up on opening device file
> > 
> > [jolsa@...va perf]$ sudo strace -p 29445
> > Process 29445 attached
> > open("/dev/snd/pcmC0D0p", O_RDONLY^CProcess 29445 detached
> > 
> > another one I recall was /dev/dri/card0 touched by X server
> > 
> > I guess those device files allow to mmap memory and we recorded
> > memory access there.. we need check for this and do not try to
> > open device files
> 
> Ok.  And that problem doesn't happen when my patch is not applied?  I am
> not sure how this patch causes open device hangs.  I'll try to run this on
> a box with X server running to duplicate.

I think it came with the memory profiling, because we treat
data areas as dsos.. open and look for symbols

jirka
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