On Thu, 31 Aug 2017 16:31:36 +0200 Vlastimil Babka <[email protected]> wrote:
> > Which version of trace-cmd failed? It parses for me. Hmm, the > > vmemmap_base isn't in the event format file. It's the actually address. > > That's probably what failed to parse. > > Mine says 2.6. With 4.13-rc6 I get FAILED TO PARSE. Right, but you have the vmemmap_base in the event format, which can't be parsed by userspace because it has no idea what the value of the vmemmap_base is. > > > > >> > >> I'm quite sure it's due to the "page=%p" part, which uses pfn_to_page(). > >> The events/kmem/mm_page_alloc/format file contains this for page: > >> > >> REC->pfn != -1UL ? (((struct page *)vmemmap_base) + (REC->pfn)) : ((void > >> *)0) > > > >> On older 4.4-based kernel: > >> > >> REC->pfn != -1UL ? (((struct page *)(0xffffea0000000000UL)) + (REC->pfn)) > >> : ((void *)0) > > > > This is what I have on 4.13-rc7 > > > >> > >> This also fails to parse, so it must be the struct page part? > > > > Again, what version of trace-cmd do you have? > > On the older distro it was 2.0.4 Right. That's probably why it failed to parse here. If you installed the latest trace-cmd from the git repo, it probably will parse fine. > > > > >> > >> I think the problem is, even if ve solve this with some more > >> preprocessor trickery to make the format file contain only constant > >> numbers, pfn_to_page() on e.g. sparse memory model without vmmemap is > >> more complicated than simple arithmetic, and can't be exported in the > >> format file. > >> > >> I'm afraid that to support userspace parsing of the trace data, we will > >> have to store both struct page and pfn... or perhaps give up on reporting > >> the struct page pointer completely. Thoughts? > > > > Had some thoughts up above. > > Yeah, it could be made to work for some configurations, but see the part > about "sparse memory model without vmemmap" above. Right, but that should work with the latest trace-cmd. Does it? -- Steve
