On Mon, Sep 30, 2013 at 6:15 PM, Peter Zijlstra <pet...@infradead.org> wrote: > On Mon, Sep 30, 2013 at 05:44:41PM +0200, Stephane Eranian wrote: >> Hi, >> >> I was alerted by people trying to use the PERF_RECORD_MMAP2 >> record to disambiguate virtual address mappings that there is a case >> where the record does not contain enough information. >> >> As you know, the MMAP2 record adds the major, minor, ino number, >> inode generation numbers to a mapping. But it does that only for >> file or pseudo -file backed mappings. That covers file mmaps and also >> SYSV shared memory segments. >> >> However there is a another kind of situation that arises in some >> multi-process benchmarks where a region of memory is cloned >> using VM_CLONE. As such, the virtual addresses match between >> the processes but the major, minor, inode, inode generation fields >> are all zeroes because there is no inode associated with the mapping. >> Yet, it is important for the tool to know the mappings between the >> processes are pointing to the same physical data. >> >> We need to cover this case and I am seeking for advice on how to >> best address this need given that we discarded using the plain physical >> address for disambiguation. > > Urgh.. who in his bloody mind is playing VM_CLNOE games that is not > pthread_creatE() ?
Some matrix multiply benchmark, I guess. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
