Re: [PATCHSET 00/17] perf report: Add -F option for specifying output fields (v4)

From: Namhyung Kim
Date: Tue May 06 2014 - 23:06:07 EST


Hi Don,

On Wed, 30 Apr 2014 09:35:55 -0400, Don Zickus wrote:
> On Wed, Apr 30, 2014 at 08:38:10AM +0900, Namhyung Kim wrote:
>> Hi Don,
>>
>> On Tue, 29 Apr 2014 13:27:35 -0400, Don Zickus wrote:
>> > On Tue, Apr 29, 2014 at 10:13:35AM +0900, Namhyung Kim wrote:
>> >> > /*
>> >> > * Addresses with no major/minor numbers are assumed to be
>> >> > * anonymous in userspace. Sort those on pid then address.
>> >> > *
>> >> > * The kernel and non-zero major/minor mapped areas are
>> >> > * assumed to be unity mapped. Sort those on address.
>> >> > */
>> >> >
>> >> > if ((left->cpumode != PERF_RECORD_MISC_KERNEL) &&
>> >> > !l_map->maj && !l_map->min && !l_map->ino &&
>> >> > !l_map->ino_generation) {
>> >> > /* userspace anonymous */
>> >> >
>> >> > if (left->thread->pid_ > right->thread->pid_) return -1;
>> >> > if (left->thread->pid_ < right->thread->pid_) return 1;
>> >>
>> >> Isn't it necessary to check whether the address is in a same map in case
>> >> of anon pages? I mean the daddr.al_addr is a map-relative offset so it
>> >> might have same value for different maps.
>> >
>> > That's why I sort on pids here. Because the anon address might have the
>> > same value for different maps. The thought was to group all the pid
>> > addresses together to keep things seperated.
>> >
>> > Do you see a different way to solve the problem? I am not sure al_addr
>> > vs. addr will make much difference here.
>>
>> I'm not saying to get rid of the pid check, I'm saying that it might
>> need to add another check for maps (i.e. start address) as there might
>> be many maps in a single address space.
>
> Hmm, I guess I would need to see an example. While I agree there might be
> many maps in a single address space (/proc/<pid>/maps demonstrates that),
> I understood them to map to a unique location (ie no overlap) unless they
> are shared.
>
> I am willing to believe I missed scenario when sorting, I just can't think
> of it (so I wouldn't know how to fix it). That's why I was looking for an
> example to make it more obvious to me. Sorry for being slow..

I'm also sorry for being late. Looking at the code, it seems to use
identity__map_ip() for anon maps so my concern is bogus. Please just
forget about it and keep going. Sorry for interrupting your work..

Thanks,
Namhyung
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