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

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Message-ID: <20140516114757.GD19475@krava.brq.redhat.com>
Date:	Fri, 16 May 2014 13:47:57 +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 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..? ;-)

# Overhead  Data Cacheline         
# ........  .......................
#
     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


jirka
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