Messages in this thread | | | Date | Thu, 16 Jun 2016 13:33:43 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v3 1/7 UPDATE2] perf tools: Find vdso with the consider of cross-platform |
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Em Thu, Jun 16, 2016 at 04:00:12PM +0300, Adrian Hunter escreveu: > On 15/06/16 16:34, Arnaldo Carvalho de Melo wrote: > > Em Tue, May 17, 2016 at 09:04:54AM +0000, He Kuang escreveu: > >> There's a problem in machine__findnew_vdso(), vdso buildid generated > >> by a 32-bit machine stores it with the name 'vdso', but when > >> processing buildid on a 64-bit machine with the same 'perf.data', perf > >> will search for vdso named as 'vdso32' and get failed. > > > > Without looking at the code, just trying to understand your patch by > > reading your description: Why would we look for names if we have > > build-ids? All this type and name comparasions seems wrong if we have a > > build-id, no? > > > > Adrian? > > We match maps to builds ids using the file name - consider > machine__findnew_[v]dso() called in map__new(). So in the context of a perf > data file, we consider the file name to be unique. > > A vdso map does not have a file name - all we know is that it is vdso. We > look at the thread to tell if it is 32-bit, 64-bit or x32. Then we need to > get the build id which has been recorded using short name "[vdso]" or > "[vdso32]" or "[vdsox32]". > > The problem is that on a 32-bit machine, we use the name "[vdso]". If you > take a 32-bit perf data file to a 64-bit machine, it gets hard to figure out > if "[vdso]" is 32-bit or 64-bit. > > This patch solves that problem. > > I acked it in another email.
Ok, somehow this got lost, I thought to have applied it already, but re-reading the changeset comment, I got confused, thanks for providing this explanation, that I will stick to the changeset log for this message, to help understanding this when scratching our heads in the future.
- Arnaldo
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