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    SubjectRe: [PATCH v1 2/2] perf tools: add attr->mmap2 support
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    On Wed, Aug 14, 2013 at 1:34 AM, Andi Kleen <ak@linux.intel.com> wrote:
    > On Tue, Aug 13, 2013 at 01:55:57PM +0200, Stephane Eranian wrote:
    >> This patch adds support for the new PERF_RECORD_MMAP2
    >> record type exposed by the kernel. This is an extended
    >> PERF_RECORD_MMAP record. It adds for each file-backed
    >> mapping the device major, minor number and the inode
    >> number. This triplet uniquely identifies the source
    >> of a file-backed mapping. It can be used to detect
    >> identical virtual mappings between processes for instance.
    >
    > Can you also add the generation number please?
    > That would make it even more unique.
    >
    I assume you're talkng about inode->i_generation, right?
    I could add that one easily. I am surprised to see:

    mm/shmem.c:
    static struct inode *shmem_get_inode(struct super_block *sb, const
    struct inode *dir,
    umode_t mode, dev_t dev, unsigned
    long flags)
    {
    inode->i_generation = get_seconds();
    }
    I am assuming that the uniqueness for SHM is coming from the SHMID and therefore
    a poor quality i_generation is sufficient here.


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