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..
Cheers,
Don
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