* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Fri, Jul 12, 2013 at 11:40:44AM +0200, Ingo Molnar wrote: > > * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > On Fri, Jul 12, 2013 at 11:15:06AM +0200, Ingo Molnar wrote: > > > > > > > > * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > > > > We need those files anyway.. The current proposal is that the entire VMA > > > > > has a single userspace pointer in it. Or rather a 64bit value. > > > > > > > > Yes but accessible via /proc/<PID>/mem or so? > > > > > > *shudder*.. yes. But you're again opening two files. The only advantage > > > of this over userspace writing its own files is that the kernel cleans > > > things up for you. > > > > Opening of the files only occurs in the instrumentation case, which is > > rare. But temporary files would be forced upon the regular usecase > > when no instrumentation goes on. > > Well, Colin didn't describe the intended use, but I can imagine a case > where its not all that rare. System health monitors might frequently > want to update this. That's true. So maybe it would be better to offer a tracepoint that allows apps to emit such information - to any system monitor around to listen. If it's made a vsyscall that does not enter the kernel if the process is not being monitored would make it very low overhead. > > So, these 400+ memory ranges are from Firefox's /proc/*/maps file: > > > <snip> > > > > It's about 35% out of 1300+ mappings that Firefox uses. > > > > It is likely that the ---p mappings (about 40 of them) are guard pages. > > > > How do I tell what the remaining anonymous areas are about? > > Well, if you'd ran it within a memory allocator debug framework that > would have kept track of this. Typically memory debuggers can keep > allocation time stacks etc. > > If I'm not actively debugging firefox I don't give a damn. Yet people are nosy and find it rather useful to have such 'heap/stack/vdso/vsyscall' annotations: 0237c000-0239d000 rw-p 00000000 00:00 0 [heap] ... 7fff622af000-7fff622d0000 rw-p 00000000 00:00 0 [stack] 7fff623fe000-7fff62400000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] and named vmas have names as well: 7fa5b02eb000-7fa5b6718000 r--p 00000000 08:03 1710237 /usr/lib/locale/locale-archive so why not allow some simple mechanism to descriptively name anonymous vmas as well? Maybe the 8 bytes shouldn't be a pointer to user-space memory, but a short string, a bit like task_struct:comm[16]? Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>