Re: [PATCH 6/6] perf: Add dcacheline sort

Don Zickus
2014-05-16T13:31:41Z

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
> # ........ .......................
> #
> 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@krava 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.

Cheers,
Don