Messages in this thread | | | Date | Mon, 12 Dec 2016 09:49:03 +0100 | From | Peter Zijlstra <> | Subject | Re: perf/jit doesn't cope well with mprotect() to jit containing pages |
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On Fri, Dec 09, 2016 at 09:02:18PM -0800, Andres Freund wrote: > > I presume the increasing MMAP2 size is triggered by the consecutive > pages being represented as a single page-range in the kernel?
Yes, we print struct vm_area_struct based information, if vmas get merged, that shows.
> If I, to work around such consecutive pages, force another page to be > mmap()ed inbetween, and avoid using MAP_ANONYMOUS, the problem also goes > away.
This would indeed inhibit vma merging.
> Am I doing something wrong, or is there a bug here?
Expected behaviour afaict
> BTW, it's also a bit weird that those MMAP2 records triggered by > mprotect/mmap, have prot set to 0...
Yes, mprotect() does: vma->vm_flags = newflags; before calling perf_event_mmap(vma); which then looks at VM_{READ,WRITE,EXEC} bits in that word to generate the prot value.
So that being 0 is a bit weird.
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